Answer:
the correct answer would be A.
Explanation:
Convert the following word equations into chemical equations using the correct
chemical formulae and physical states.
Reactions involving ionic compounds
1. Aluminium sulfate solution + lithium hydroxide solution → aluminium hydroxide
solid + lithium sulfate solution
2.Ammonium carbonate solution+ magnesium chloride solution→ammonium chloride solution + magnesium carbonate solid
Please reply ASAP, thanks!:)
Answer:
Below.
Explanation:
1. Al2(SO4)^3 (aq) + 6LiOH aql) ----> 3Li2SO4 (aq) + 2Al(OH)^3 (s)
2. (NH4)2CO3 (aq) + MgCl2 (aq) ----> 2(NH4)Cl (aq) + MgCO3 (s).
Chemical equations are represented using correct formulas and physical states, with the aluminum sulfate and lithium hydroxide reaction yielding aluminum hydroxide and lithium sulfate, and the ammonium carbonate and magnesium chloride reaction producing ammonium chloride and magnesium carbonate.
Explanation:To convert word equations into chemical equations, it is essential to use correct chemical formulas and include the physical states of the compounds. Here are the given reactions converted into chemical equations:
Aluminium sulfate solution reacts with lithium hydroxide solution to form an aluminium hydroxide solid and a lithium sulfate solution: 3LiOH(aq) + Al2(SO4)3(aq) → 2Al(OH)3(s) + 3Li2SO4(aq)Ammonium carbonate solution reacts with magnesium chloride solution to form an ammonium chloride solution and a magnesium carbonate solid: (NH4)2CO3(aq) + MgCl2(aq) → 2NH4Cl(aq) + MgCO3(s)Ensuring the reaction equations are balanced is crucial for accurately representing the conservation of mass in chemical reactions.
.92 moles of carbon dioxide, CO2, was produced when you burned C6H120. (glucose) with O2.
How many grams of water was also produced?
CGH 120(s) + 6 O2(g) – 6 CO2 (g) + 6 H20 (8)
O moles to moles
moles to mass
mass to moles
mass to mass
Answer:
16.56g.
Explanation:
You need to compare the number of coefficient of the reaction product to find how much water produced. The reaction formula will produce 6 carbon dioxide(CO2) and 6 water (H2O).
If the reaction produces 0.92 moles of carbon dioxide, then the amount of water produced in moles will be: 0.92 moles * (6/6)= 0.92 moles
The molar mass of water is 18g/mol, so the calculation of moles to mass will be: 0.92 moles * (18g/mol)= 16.56g.
0.500 g of a sample which contains copper is analyzed iodometrically. Copper (II) is reduced to copper (I) by the iodide. What is the percent copper in the sample if 20.00 cm3 of 0.1 M sodium thiosulphate solution is required for the titration of the liberated iodine?
Answer:
%Copper = 25.42 %
Explanation:
For solving this problem one first write down the half reactions as;
Reduction of Cu²⁺ to Cu⁺¹ by I⁻:
2 Cu²⁺ + 4 I⁻ → 2 CuI + I₂
Secondly, the titration reaction between Na₂S₂O₃ with I₂ as;
2 S₂O₃²⁻ + I₂ → S₄O₆²⁻ + 2 I⁻
Now, Calculate Moles of S₂O₃²⁻ as;
Moles = Molarity × Volume
Putting values,
Moles = 0.1 mol/L × 0.02 L
Moles = 0.002 moles of S₂O₃²⁻
From first two equations we can conclude that,
2 moles of S₂O₃²⁻ liberated I₂ produced by = 2 moles of Cu²⁺
So,
0.002 moles of S₂O₃²⁻ will liberate I₂ produced by = X moles of Cu₂⁺
Solving for X,
X = 0.002 mol × 2 mol / 2 mol
X = 0.002 mol of Cu²⁺
So, we require 0.002 moles of Cu²⁺ to produce I₂ enough for titrating with 0.1 M (20.00 mL) sodium thiosulphate solution.
Now, Calculate mass of Copper as,
Mass = Moles × A.Mass
Mass = 0.002 mol × 63.55 g/mol
Mass = 0.1271 g of Copper
Lastly, calculate % copper as,
%Copper = 0.1271 g / 0.500 g × 100
%Copper = 25.42 %
Final answer:
To calculate the percent copper in a sample using iodometric titration, the amount of sodium thiosulphate used in the titration reveals the moles of copper present. The mass of copper is then calculated, allowing us to find that the sample is 25.42% copper.
Explanation:
To determine the percent copper in the sample using iodometric titration, we first need to understand the chemistry involved. The reaction between Copper (II) and iodide produces iodine, which is then titrated with sodium thiosulphate. The formula for calculating the percent copper is based on the stoichiometry of these reactions.
Given that 20.00 [tex]cm^3[/tex] of 0.1 M sodium thiosulphate is required, we can calculate the moles of sodium thiosulphate reacted: Moles of sodium thiosulphate = 20.00 [tex]cm^3[/tex] × 0.1 mol/L = 0.0020 mol.
Sodium thiosulphate reacts with iodine in a 1:1 molar ratio, meaning 0.0020 mol of iodine was produced. The stoichiometry between copper (II) and iodine is also 1:1, so 0.0020 mol of Copper (II) was initially present. The molar mass of Copper (II) is 63.546 g/mol, hence the mass of copper in the sample is 0.0020 mol × 63.546 g/mol = 0.1271 g.
To find the percent copper, we then use the formula: Percent Copper = (Mass of Copper in the Sample / Total Mass of the Sample) × 100 = (0.1271 g / 0.500 g) × 100 = 25.42%.
The gas carbon dioxide is a pure substance. Which of the following is true about carbon dioxide ?
Carbon and oxygen are chemically bonded in it.
Carbon and oxygen retain their original identity in it
It can be separated into carbon and oxygen using physical methods
The proportion of carbon and oxygen is different in different samples of the gas
Answer:
Carbon and oxygen are chemically bonded in it.
Explanation:
The other answer choices do not apply for compounds, but rather for mixtures instead.
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No matter where it was collected, carbon dioxide has a constant composition, making it a pure substance. One carbon atom and two oxygen atoms are always present in each carbon dioxide molecule. Thus, option A is correct.
What is pure carbon dioxide gas?Two oxygen atoms are covalently bound to one carbon atom to form the chemical molecule known as carbon dioxide (CO2). It exists as a gas in the Earth's atmosphere at standard pressure and temperature.
The production and burning of fossil fuels like coal, oil, and natural gas as well as during wildfires and other natural processes like volcanic eruptions.
Inhaling CO2 is thought to be only mildly harmful. The fundamental health impacts of CO2 are a result of its simple asphyxia nature.
A gas that decreases or replaces the natural oxygen in breathing air is referred to as a simple asphyxia. Mild CO2 exposure symptoms can include headache and sleepiness.
Therefore, Carbon and oxygen are chemically bonded in it.
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the graph system represents the rate in which two trucks are being filled where X represent the time in minutes and Y represents the percentage filled
Answer:
Ok so I seen your comment because I was looking up the answer and couldn’t find it anywhere so I risked to see if I got it wrong and got it right the answer is b on Plato and sorry I don’t know what it said but I do know I clicked on b hope this helps
Explanation:
Answer:
B.
The solution is nonviable because the time cannot be negative.
Explanation:
If it's wrong tell me
What are the four main reservoirs of carbon
the atmosphere,the terrestrial biosphere, the oceans and the sediments
formula for sodium iodine
Answer:
NaI
Explanation:
The formula for sodium iodide is NaI
It is a compound (ionic compound) formed by the chemical reaction between sodium, Na and iodine.
The sodium is a metal in group 1 with atomic number 11 and mass number 23 ,it has one valence electron which it gives out to form a cation of +1 charge and the iodine is in group 7(halogen family) with atomic number 57 and mass number 23 and it has 7 valence electrons which allows it attract 1 electron to form an anion(iodide) of charge -1.
The reaction of sodium ion with iodide ion form the sodium iodide where sodium releases its one valence electron and iodine receives it which makes it balance that is they react in ratio 1:1 and thus have a chemical formula of NaI.
NaI has atomic mass of 150g/mole that is 127 + 23 = 150
Where
Na=23g/mol, I = 127g/mol
NaI is used mainly as nutritional supplement
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Which of the following characteristics did john Dalton include in his description of the atom?
can be more than one.
A. Atoms are smaller than quarks.
B. In any element all the atoms are the same.
C. Atoms exist only on Earth
D. All matter is made up of atoms.
E. Elements in a compound are always in a constant ratio.
All matter is made up of atoms is the characteristics that John Dalton included in his description.
Explanation:
Atom is said to be the smallest particle that has the positively charged proton and negatively charged electron and no charge neuton iht the nucleus at the center. It is an origin for the all element formation . in an element all atoms are maximum identical that's why they are difficult to divide and destruct. John Dalton stated that all matters consist of atoms which are said to be the smallest thing .At 1400 mm Hg, a gas has a volume of 350L. What is it volume at stander pressure?
Answer:
V₂ = 630 L
Explanation:
Given data:
Initial volume = 350 L
Initial pressure = 1400 mmHg (1400/760 = 1.8 atm)
Final volume = ?
Final pressure = standard = 1 atm
Solution:
The given problem will be solved through the Boly's law,
"The volume of given amount of gas is inversely proportional to its pressure by keeping the temperature and number of moles constant"
Mathematical expression:
P₁V₁ = P₂V₂
P₁ = Initial pressure
V₁ = initial volume
P₂ = final pressure
V₂ = final volume
Now we will put the values in formula,
P₁V₁ = P₂V₂
1.8 atm × 350 L = 1 atm × V₂
V₂ = 630 atm. L/1 atm
V₂ = 630 L
To find the volume of gas at standard pressure, use Boyle's Law. Given an initial pressure of 1400 mm Hg and volume of 350L, at standard pressure (760 mm Hg) the volume would be 500L.
Explanation:To determine the gas volume at standard pressure when given a volume at a different pressure, we can use Boyle's Law, which states that the product of pressure and volume is constant for a given amount of gas at a constant temperature (P1V1 = P2V2). Standard pressure (STP) is defined as 1 atm, which is equivalent to 760 mm Hg. The volume of the gas at STP can thus be calculated using the initial conditions:
V2 = (P1 * V1) / P2
Substitute the provided values:
P1 = 1400 mm Hg
V1 = 350 L
P2 = 760 mm Hg (standard pressure)
Now, rearrange the equation to solve for V2:
V2 = (1400 mm Hg * 350 L) / 760 mm Hg = 500 L
Thus, the volume of the gas at standard pressure would be 500 L.
Which phrase best describes the main reason scientist perform experiments
Answer: an experiment is an empirical procedure that arbitrates competing models or hypotheses. Researchers also use experimentation to test existing theories or new hypotheses to support or disprove them.
Explanation: I don't know if this helps but if it does let me know.
Final answer:
Scientists perform experiments primarily to test hypotheses, gather data, and validate or disprove their proposed explanations for phenomena. These experiments are essential for the advancement of scientific knowledge and are often peer-reviewed and published if the results are significant.
Explanation:
The main reason scientists perform experiments is to test a hypothesis which is a proposed explanation for a phenomenon, and to answer specific research questions. Experiments are carefully designed to collect data and analyze results objectively. If the results support the hypothesis, further experiments may be conducted to test related hypotheses, or if the results are inconsistent with the hypothesis, it may be discarded for a new alternative hypothesis.
By performing experiments, scientists aim to ensure repeatability and to explore underlying causes for observed phenomena. Experiments are a critical aspect of the scientific method, enabling researchers to extend their knowledge of the natural universe through empirical evidence. The design of an experiment is guided by the goal to make measurements that test the hypothesis, and often involves statistical, mathematical, or graphical analysis of the data collected.
Significant results get published in scientific journals, which serve to communicate the findings and contribute to the body of scientific knowledge. With the advent of open access and electronic journal availability, the dissemination of scientific knowledge has become more accessible.
3. Which plane’s velocity was greatest?
Answer:
North American X-15
Explanation:
This is the fastest manned aircraft
Answer: SR-71 Blackbird
Explanation: The fastest manned plane is the SR-71 Blackbird. It has traveled at 936 m/s. That is about three times the speed of sound, Mach 3. The SR-71 Blackbird set records both speed and altitude. (brainliest answer pls <3)
How many molecules of water are present in 7.9 g of water
Answer:
The number of molecules = 2.6408 molecules
Explanation:
To determine the number of molecules in water, we need to determine how many moles of water we have
Water has a molar mass of 18.015g/mol, this means that one mole of water molecules has a mass of 18.015g
To find the number of molecules,
7.9g * 1 mole H2O/ 18.015g
= 0.4385mole of H2O
Using avogadro number,
0.4385 H2O * 6.022* 10^23molecules/ 1 mole of H2O
That's 0.4385 H2O multipled by 6.022*10^ 23 molecules divided by 1 mole of H2O
Which gives == 2.6408 molecules
20 POINTS !!!
Based on Gay-Lussac's law, which of the following statements is true for an ideal gas at constant volume and mole amount?
a - the number of collisions is independent of pressure
b - the number of collisions decreases with increase in pressure
c - pressure is directly proportional to the absolute temperature
d - pressure is inversely proportional to the absolute temperature
C. pressure is directly proportional to the absolute temperature
Explanation:
Gay- Lussac's law is defining a relationship between the pressure and temperature at a constant volume for an ideal gas.The law says that when there is an increase in the temperature of the ideal gas then the pressure of the gas is also increasing. There created a direct relationship between temperature and pressure. Option A tells us that collision and pressure are not related which is not true, Option B is saying that as pressure increases the collisions of the gas particles decreases which is not correct, Option C is drawing the correct relationship between pressure and temperature, and option D is talking the reverse of option C which is incorrect. Hence, the answer is CAnswer:
C. Pressure is directly proportional to the absolute temperature.
Explanation:
I took the test :)
Name one way igneous rock is different from metamorphic rock.
Answer:
Metamorphic rock is classified by texture and composition. The texture of a metamorphic rock can be either foliated and appear layered or banded, or non-foliated and appear uniform in texture without banding. Foliated rocks contain many different kinds of minerals, but non-foliated rocks contain only one main mineral, which contributes to their more uniform appearance. Igneous rocks are classified according to mode of occurrence, texture, mineralogy, chemical composition, and the geometry of the igneous body.
Explanation:
Consider the reaction of hydrogen gas with chlorine gas:
H2 + Cl2 → 2HCl
4 molecules of hydrogen gas react with 6 molecules of chlorine gas.
4 molecules of hydrogen gas in this reaction will produce 8 molecules of HCl.
6 molecules of chlorine gas in this reaction will produce 12 molecules of HCl.
Hydrogen is the limiting reactant.
All BUT ONE statement about limiting reactants and reactants in excess is true. That is
A) when the limiting reactant runs out, the reaction stops.
B) the limiting reactant produces the least amount of product.
C) the reactant in excess produces the greatest amount of product.
D) when the reaction stops due to the limiting reactant, there will be some of the excess reactant left over.
Answer: C
Explanation: The answer is c because of the H2+CI1--> 2HCI
How do you do a stoichiometric problem
Write the balanced chemical equation.
Convert the units of the given substance (A) to moles.
Use the mole ratio to calculate the moles of wanted substance (B).
Convert moles of the wanted substance to the desired units.
Calcium nitrate + aluminum hydroxide balanced equation
Answer:
Al(NO3)3 + Ca(OH)2 = Al(OH)3 + Ca(NO3)2.
Explanation:
The balanced equation for the reaction between calcium nitrate and aluminum hydroxide is: Ca(NO3)2 + 2Al(OH)3 → 2Al(NO3)3 + 3Ca(OH)2.
Explanation:The balanced equation for the reaction between calcium nitrate and aluminum hydroxide is:
Ca(NO3)2 + 2Al(OH)3 → 2Al(NO3)3 + 3Ca(OH)2
In this reaction, calcium nitrate reacts with aluminum hydroxide to produce aluminum nitrate and calcium hydroxide.
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witch equations are correctly balanced.
H 2 O + 2O 2 H 2 O 2
Fe 2 O 3 + 3H 2 2Fe + 3H 2 O
Al + 3Br 2 AlBr 3
CaCO 3 CaO + CO 2
Answer:
2nd and last.
Explanation:
In the first equation,the number of hydrogen atoms is not balanced and in the third,the number of aluminum atoms is not balanced.
Answer:
1. Fe 2 O 3 + 3H 2 2Fe + 3H 2 O
2. CaCO 3 CaO + CO 2
14. Classify Identify each molecule below as
either a polar molecule or a nonpolar molecule. Explain your reasoning.
Oxygen
Carbon dioxide
Answer:
Oxygen - non polar
Carbon Dioxide - non polar
Explanation:
Oxygen is non polar because it is a covalent bond with equal electronegativity.
Carbon dioxide is also non polar because it has 2 Oxygen atoms which are as I stated above they are equally electronegative.
Oxygen is a nonpolar molecule as it consists of two identical atoms sharing electrons equally. Carbon dioxide is also nonpolar because, despite having polar covalent bonds, its linear shape causes the partial charges to cancel each other out.
The question asks whether each given molecule, oxygen, and carbon dioxide is polar or nonpolar and to explain the reasoning behind the classification. The polarity of a molecule is determined by both the electronegativity of the atoms and the overall molecular geometry. Oxygen (O2) is a homonuclear diatomic molecule, meaning it consists of two identical atoms that share the electrons equally, and as a result, it is a nonpolar molecule.
Carbon dioxide (CO2), on the other hand, is a linear molecule with two polar covalent bonds between carbon and oxygen. However, due to the symmetry of its linear shape, the partial charges on the molecule cancel each other out, making it a nonpolar molecule.
Which of the following is true for a cell that has a nucleus?
A. It will not have nuclear membrane. B. It will not have a nucleolus. C. It will not have ribosomes. D. It will not have a nucleoid.
Answer:
D. It will not have a nucleoid.
Explanation:
Cells with a nucleus are eukaryotic cells. This means they will have membrane-bound organelles. The nucleus is an example of a membrane bound organelle that houses the DNA.
A. It will not have nuclear membrane. - this is false, the nucleus is surrounded by the nuclear membrane
B. It will not have a nucleolus - this is false, the nucleolus is a part of the nucleus, usually where ribosomal RNAs are made
C. It will not have ribosomes - this is false, proteins are made in ribosomes and they are present in all cells
D. It will not have a nucleoid - this is true. The nucleoid is a space in the cytoplasm of prokaryotic cells that houses the DNA. It is not membrane bound, and is distinct from the nucleus.
Answer:
top answer is right for sur!
HAVE A GOOD DAY!!
Explanation:
Low air pressure can cause
Question 5 options:
clouds and precipitation to form
the temperature to drop
a sunny day
fog
Answer: clouds and precipitation to form
Explanation: In a low pressure system warm air rises into the atmosphere and cools down and forms cloud. In low air pressure the humidity is high since there is enough space for water vapor to occupy causing precipitation.
Fe + _ H2SO4 _ Fe2(SO4)3 + _ H2
How do water molecules dissolve a salt?
O
A. The water molecules move around the salt crystals.
O
B. The water molecules separate the crystals into molecules.
O
C. The water molecules move around the salt ions.
D. The salt crystals squeeze in between water molecules.
The correct answer is B) The water molecules separate the crystals into molecules.
What's a molecule?The smallest particle of a substance that has all of the physical and chemical properties of that substance. Molecules are made up of one or greater atoms.
What are the kinds of molecules?Diatomic Molecules -- A diatomic atom consists of the most effective atoms, of equal or distinctive chemical factors. Heteronuclear Diatomic Molecules -- A heteronuclear diatomic molecule consists of atoms of equal detail mixed. OXYGEN MOLECULE.CARBON MONOXIDE MOLECULE (CO)How does water dissolve salt?
Water dissolves in salt because the terrible part of a water molecule, the oxygen part is interested in the wonderful sodium ion of the salt. also, the effective part of the water molecule, the hydrogen component is drawn to the terrible chloride ion of the salt. Water molecules pull the sodium and chloride ions aside, breaking the ionic bond that held them together. After the salt compounds are pulled apart, the sodium and chloride atoms are surrounded via water molecules. once this occurs, the salt is dissolved, ensuing in a homogeneous solution.
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Answer:
it’s C
Explanation:
How many moles of oxygen are needed to react with 23.8 moles of aluminum?
Answer:
17.85moles
Explanation:
Check attachment
If an atom has three protons three neutrons and two electrons what is the electrical charge of the atom
Answer:
+1
Explanation:
From the question, the following were obtained:
Proton = 3
Neutron = 3
Electron = 2
From the above, we see clearly that the atom has loss 1 electron as the electron is lesser than the proton with 1. So, the atom has a charge of +1
The electrical charge of an atom is determined by subtracting the number of electrons from the number of protons. In this atom with three protons and two electrons, the overall charge is +1.
Explanation:When considering the electrical charge of an atom, the important components to consider are the protons, which have a positive charge, and the electrons, which have a negative charge. Neutrons do not have a charge, so they do not contribute to the overall charge of the atom. In this case, the atom has three protonsand two electrons. Each proton has a charge of +1, and each electron has a charge of -1. Therefore, the overall charge of this atom is calculated by subtracting the number of electrons from the number of protons: 3 (protons) - 2 (electrons) = +1. So this atom has an overall charge of +1.
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why do we consider diamonds a kind of metamorphic rock?
Final answer:
Diamonds are considered a metamorphic rock because they are formed through intense heat and pressure deep within the Earth's mantle, which transforms carbon into a crystalline structure. Unlike other metamorphic rocks that show foliation, diamonds are non-foliated as they consist of a single mineral.
Explanation:
We consider diamonds a kind of metamorphic rock because they are formed deep within Earth's mantle through a process of intense heat and pressure. This process transforms the carbon atoms into a crystal structure known as a diamond. Metamorphism involves the recrystallization of minerals and can lead to the formation of new minerals, the reorientation of minerals due to pressure, and sometimes the migration of ions within crystal structures due to heat. While most metamorphic rocks are found in mountain belts or ancient mountain belts due to the conditions conducive to metamorphism, diamonds are actually formed at much greater depths and require unique conditions including temperatures around 900 to 1,300 degrees Celsius, and pressures over 45 kilobars.
The formation of metamorphic rocks, including diamonds, is a facet of the rock cycle, and these transformations allow rocks to become stable under new environmental conditions. Unlike most metamorphic rocks that exhibit foliation due to the reorientation of minerals, diamonds do not show foliation as they are a single mineral rock, thus they are considered non-foliated. They are created from a single element, carbon, and although they have a different formation process compared to foliated metamorphic rocks, the principles of temperature and pressure still apply in their creation.
How do I do balancing equations
Answer:
1 Count the atoms of each element in the reactants and the products. 2 use coefficient place them in front of the compound as needed.
Please solve this a,b,c,d
Answer:
The answer should br C
Explanation:
Which equation has both a liquid and a gas as products? 2 upper H g upper O (s) right arrow 2 upper H g (l) plus upper O subscript 2 (g). 2 upper M g (s) plus upper O subscript 2 (g) right arrow 2 upper M g upper O (s). 1 UJpper K upper C l upper O subscript 3 (s) right arrow 2 upper K upper C l (s) plus 3 upper O subscript 2 (g). Upper M g (s) plus 2 upper H upper C l (a q) right arrow upper H subscript 2 (g) plus upper M g upper C l subscript 2 (a q).
Answer:
A
Explanation:
Consider the following intermediate chemical equations.
What is the enthalpy of the overall chemical reaction?
-205.7 kJ
-113.4 kJ
-14.3 kJ
78.0 kJ
Answer:
The first choice, [tex]-205.7\; \rm kJ[/tex].
Explanation:
Let the three reactions, where the enthalpy change were known, be called (1), (2), and (3).
The goal is to find the enthalpy change of the fourth equation. Assume that this equation can be written as [tex]x \times (1) + y \times (2) + z \times (3)[/tex] for some [tex]x[/tex], [tex]y[/tex], and [tex]z[/tex] (might not be whole numbers or take positive values.) Then, by Hess's Law, the enthalpy change of that reaction would be [tex]x \cdot \Delta H_1 + y \cdot \Delta H_2 + z \cdot \Delta H_3[/tex].
To find these [tex]x[/tex], [tex]y[/tex], and [tex]z[/tex], consider: what combination of reaction (1), (2), and (3) would give the fourth reaction?
Imagine that the coefficients are positive for all the reactants, and negative for all the products.
For example: in (1), [tex]\rm H_2\; (g)[/tex] has a coefficient of [tex]2[/tex]. However, since it is on the the product side of (1), its value should be [tex]-2[/tex]. Also, in (3)
Since there is no [tex]\rm H_2\; (g)[/tex] in the desired equation, the value of [tex]x[/tex], [tex]y[/tex], and [tex]z[/tex] should ensure that [tex]-2x + z = 0[/tex].
Another example: [tex]\rm CH_4\; (g)[/tex] is on the reactant side of the first reaction. Its coefficient in the equation is [tex]1[/tex], so that corresponds to [tex]+1[/tex]. Since [tex]\rm CH_4[/tex] is neither in (2) nor in (3), the value of
In the desired equation, [tex]\rm CH_4\; (g)[/tex] is on the reactant side with a coefficient of [tex]1[/tex]. As a result, the value of [tex]x[/tex], [tex]y[/tex], and [tex]z[/tex] should ensure that [tex]x = 1[/tex].
One such equation can be found for each species in the reactions.
[tex]\displaystyle \begin{cases}x = 1 & \left(\text{For $\mathrm{CH_4\; (g)}$}\right) \\ -x - y= 0 & \left(\text{For $\mathrm{C\; (s)}$}\right) \\ -2\, x + z = 0 & \left(\text{For $\mathrm{H_2\; (g)}$}\right) \\ y = -1 & \left(\text{For $\mathrm{CCl_4\; (g)}$}\right) \\ -2\, y + z= 4 & \left(\text{For $\mathrm{Cl_2\; (g)}$}\right) \\ -2\, z = -4 & \left(\text{For $\mathrm{HCl\; (g)}$}\right)\end{cases}[/tex].
Solve this system of equations for [tex]x[/tex], [tex]y[/tex], and [tex]z[/tex] (this approach works only if at least one solution exists.) In this case,
[tex]\displaystyle \begin{cases}x = 1 \\ y = -1 \\ z = 2\end{cases}[/tex].
Calculate the enthalpy change of the desired reaction:
[tex]\begin{aligned}\Delta H &= x\times \Delta H_1 + y \times \Delta H_2 + z \times \Delta H_3 \\ &= 1 \times 74.6 + (-1) \times 95.7 + 2 \times (-92.3) \\ &= -205.7\; \rm kJ\end{aligned}[/tex].