There are several steps involved in practicing stoichiometry problems and proper knowledge of these steps will help guide us through the basics of stoichiometry.
I will want to lay down some basic rules in solving stoichiometry questions and how to solve the stoichiometry step by step.
An easy step by step of 50 Stoichiometry Practice questions
So, the rules I want to give you are simple and you only need to master them by looking at the couple of stoichiometry questions and following the step by step method of solving stoichiometry problems..
I will summarize succinctly few steps required for solving stoichiometry.
- Understand how to write a balanced chemical equation: Before solving any stoichiometry problem, you need to ensure that the chemical equation is balanced. This means that the number of atoms of each element on both the reactant and product side is the same. It is important to note that without a balanced chemical equation, it will not be possible to really determine the correct ratios of reactants and products.
- Then convert the number of reactants and products to moles: Stoichiometry calculations are based on the number of moles of reactants and products involved in a chemical reaction. Therefore, it is important to convert any given quantities of substances to moles. This can be done using the molar mass of the substance.
- Compare the mole ratios: The mole ratios are the coefficients in a balanced chemical equation and these mole ratios between the reactants and products are the background information used in balancing chemical equations. These ratios can be used to determine the moles of one substance based on the moles of another substance.
- Then you convert the moles to desired units: Immediately you have determined the moles of the substances involved in a chemical reaction, then you must convert these values to the desired units. These may include converting to mass, volume, or concentration, depending on the problem you’re solving.
- Crosscheck your work: Finally, it is important to crosscheck your works and your answer to ensure that it makes sense and is consistent with the laws of chemistry. Double-check your calculations and make sure that your answer is reasonable based on the context of the problem.
If 2.3 moles of iron III oxide react with carbon, Calculate the moles of carbon iv oxide according to this equation; 2Fe2O3+3C—>4Fe+3CO2
The balanced chemical equation shows that 2 moles of iron III oxide react with 3 moles of carbon to produce 3 moles of carbon IV oxide.
So, we need to first calculate the moles of iron III oxide that react, which is given as 2.3 moles.
Using the stoichiometry of the balanced equation, we can set up a proportion:
2 moles Fe2O3 =========3 moles CO2
2.3 moles Fe2O3 ========= x moles CO2
To solve for x, we can set up the following proportion:
2.3 moles Fe2O3 x 3 moles of CO2/2
Cross-multiplying, we get:
x = 3.45 moles CO2
Therefore 3.45 moles of carbon IV oxide would be evolved
If 4 moles of methane reacted, calculate the volume of carbon ii oxide evolved by incomplete combustion of methane;
2CH4 + 3O2 —> 2CO + 4H2O
2CH4 + 3O2 —> 2CO + 4H2O
From the mole ratio
2 moles of CH4===== 2 moles of CO
4 moles of CH4====== x
X = 4 x 2/2 = 4 moles of CO
At standard temperature and pressure
1 mole of CO ===22.4 dm3/L
4 moles of CO==== x
X = 4 x 22.4 = 89.6 dm3 of CO
So, the volume of CO evolved at stp is 89.6 dm3
You will notice that I did compare mole ratios first before converting to any desired quantity required.
Also, I didn’t bother trying to determine the limiting reagent because I was given only one reactant which is assumed the limiting reagent.
If 2.5 moles of magnesium nitride react, what volume ammonia would be evolved
Mg3N2 + 3H2O —> 3MgO + 2NH3
Compare the mole ratio of these two substances mentioned
1 mole of Mg3N2 =======2 moles of NH3
2.5 moles of Mg3N2 ======= x
X = 2.5 x 2/1= 5 moles of NH3
Then convert moles to volume
1 mole of NH3=== 22,4 dm3
5 moles of NH3 ====X
X = 5 X 22.4 =112 dm3
What mole of vanadium iii oxide would be evolved by reacting 2.5 moles of vanadium
2V2 + 3O2===2V2O3
2 moles of Vanadium ===== 2 moles of Vanadium III oxide
2.3 moles of Vanadium ===== x
X = 2.3 x2 /2 = 2.4 moles of vanadium iii oxide
What mass of aluminum chloride would be produced by the reaction of 4.5 moles of aluminum with hydrochloric acid?
3Al + 6HCl ====2AlCl3 + 3H2
Calculate the mass of Aluminum chloride produced by the reaction?
3 moles of Aluminum ====== 2 moles of Aluminum chloride
4.5 moles of Aluminum =====X
X= 4.5 x 2/3 = 3 moles of Aluminum chloride
So, you can convert the mole to mass
1 mole of AlCl3 ======= 133.5 g
3 moles of AlCl3 ===== x
X = 3 x 133.5 =400.5 grams of AlCl3
Though i will be updating the post to 50 stoichiometry problems