How Do I Solve Gas Stoichiometry Problems?
Stoichiometry gas problems involves different categories and also involve gas stoichiometry, but the approach used same.
There is a step-by-step way of solving stoichiometry problems which is still the same for stoichiometry involving gases.
What’s gas stoichiometry?
Gas stoichiometry is the simply the particular stoichiometry concept that deals with gases in a balanced chemical equation.
In solving gas stoichiometry, it is still valid to recall that stoichiometry can be done very easily especially if you follow the rules.
The simple rules include;
- Write a balanced chemical equation
- Compare the mole ratios of reactants and products in the balanced chemical equation
- Use the known substance to determine the unknown substance
I’m going to work you through some examples of gas stoichiometry problems.
Yes, I’m aware of some gas stoichiometry problems involving Ideal gas law since temperature and pressure are at different conditions.
I’m going to show all the possible stoichiometry problems.
Gas Stoichiometry Problems
Actually, the gas stoichiometry solved problems is just to lay emphasis on the simple steps involved in solving stoichiometry.
Task 1
N2 + 3H2====2NH3
If 3.4 moles of Nitrogen react with excess Hydrogen.
Calculate the mole and volume of ammonia evolved.
Solution
N2+ 3H2===2NH3
Check if the chemical equation is balanced
Compare the mole ratio of Nitrogen and ammonia
1 mole of N2===2 moles of NH3
3.4 moles of N2===X
X= 3.4 X 2 /1 = 6.8 moles of NH3 evolved
Volume evolved
You can use stoichiometry conversion here
If 1 mole of NH3===22.4dm3
6.8 moles of NH3==X
X= 6.8 X 22.4 =152.32 dm3 of ammonia evolved
Task 2
Calculate the mole and mass of carbon iv oxide evolved from the reaction of 2 3 moles of Hydrochloric acid and calcium carbonate .
Check if the chemical equation is balanced
Compare the mole ratio of Hydrochloric acid and calcium carbonate
CaCO3 + 2HCl====CaCl2 + H2O + CO2
Solution
CaCO3 + 2HCl===CaCl2+ H2O +CO2
2 moles of HCl===1 mole of CO2
2.3 moles of HCl=== X
X= 2.3 /2= 1.15 mole of CO2
So, you use stoichiometry conversion to change to mass
I mole of CO2 == 44 grams
1.15 moles of CO2 == X
X= 1.15 X 44 =50.6 grams of carbon iv oxide
Task 3
If 4.5 moles of zinc react with Hydrochloric acid.
Calculate the mole and volume of hydrogen evolved according to this equation.
Zn + 2HCl====ZnCl2 + H2
solution
1 mole of Zn ==== 1 mole of H2
4.5 moles of Zn===X
X== 4.5 X 1 /1
X= 4.5 moles of Hydrogen
Since 1 mole of H2==22.4 dm3
4.5 moles of H2==X
X= 4.5 X 22.4 = 100.8dm3 of Hydrogen gas
Task 4
If 15.8g of magnesium reacts with Zinc Chloride
Calculate the mole , mass and volume of chlorine evolved .
Mg + ZnCl2 ===MgCl2 + Cl2
Solution
1 mole of Mg ==1 mole of Cl2
Change mass to mole
I mole of Mg==24 grams
X ==15.8 grams
X== 1 mole X 15.8 / 24
X==0.658 mole of Mg
Comparing the moles
1 mole of Mg ==1 mole of Cl2
0.658 mole of Mg== X
X= 0.658 X 1 = 0.658 mole of Chlorine
Converting to volume
1 mole of Cl2=== 22 4 dm3
0.658 mole of Cl2== X
X== 0.658 X 22.4
X=14.74 dm3 if Chlorine
Converting to mass
1 mole of Cl2== 71 grams
0.658 mole of Cl2== X
X= 0.658 X 71
X=46.72 grams of Chlorine gas
Task 5
If 3.3 moles of Nitrogen burnt in oxygen at stp according to this equation
N2 + O2===2NO
Calculate the volume of Nitrogen ii oxide at 660mmHg and 13.6 C.
Solution
Using the equation of reaction
At stp
1 mole of N2 ===2 moles of NO
3.3 moles of N2 ==X
X= 3.3 X 2 /1 = 6.6 moles of Nitrogen II oxide
Convert to volume
1 mole of NO== 22.4 dm3
6.6 moles of NO=X
X= 6.6 x22.4 =147.84 dm3
Using general gas equation
P1V1/T1= P2V2/T2
V2= P1V1T2/P2T1
Using the data
P1 =760 mmHg
V1=147.84 dm3
T1= 273K
P2=660 mmHg
T2=286.6K
V2=?
Substituting the values
V2= P1V1T2/P2T1
V2= 760x 147.84x 286.6/600× 273
V2=760× 147.84×286.6/600×273
V2=196.6 dm3
So, in general gas stoichiometry is very crucial in general stoichiometry but the only important thing is that it involves quantities of gaseous reactants and products.
