Try It
Let's practice finding the molar mass of some compounds. Perform the calculation and check your answers. Remember to round to the nearest hundredth.
- What is the molar mass of LiCl?
Answer: 42.39g
Here is how to solve for the molar mass of LiCl:
Li 1 x 6.94 = 6.94g
Cl 1 x 35.45 = 35.45g
6.94g + 35.45g = 42.39g
The molar mass of LiCl is 42.39g.
- What is the molar mass of K2SO4?
Answer: 174.28g
Here is how to solve for the molar mass of K2SO4:
K 2 x 39.09 = 78.18g
S 1 x 32.1 = 32.1g
O 4 x 16.0 = 64.0g
78.18 + 32.1 + 64.0 = 174.28g
The molar mass of K2SO4 is 174.28g.
- What is the molar mass of the products in the following balanced equation:
CH4 → C + 2H2Answer: 16.0g
Here is how to solve for the molar mass of the products in the following balanced equation:
CH4 → C + 2H2
C 1 x 12.0 = 12.0g
H 2 x 1.0 = 2.0g
There are 2 H2 so 2.0g x 2 = 4.0g total
12.0 + 4.0 = 16.0g of products
The molar mass of the above balanced equation is 16.0g.
- If the mass of the products is 16.0g, what should the mass of the reactants be? For the same equation:
CH4 → C + 2H2
Answer: 16.0g
The mass of the reactants should be the exact same as the mass of the products because mass is conserved in a chemical reaction.
Now let's use what we know about molar mass to find the mass of the reactants or products of a chemical equation. Perform the calculation and enter your answer in the box.