C5 - Moles and molar mass

Question 1

What is the unit for molar mass?

Answer 1

g/mol

Question 2

Work out the molar mass of:
nitrogen gas, N2
chlorine gas, Cl2

Answer 2

Nitrogen = 14 + 14 = 28 g/mol
Chlorine = 35 + 35 = 70 g/mol

Question 3

What is the formula for number of moles?

Answer 3

number of moles = mass/molar mass

Question 4

What mass of carbon dioxide is formed when 100g of C7H16 is burned?

Answer 4

m = molar mass x number of moles
molar mass of C7H16 = 12 x 7 + 16 x 1 = 100g
molar mass of CO2 = 1 x 12 + 2 x 16 = 44g
from the equation 1 mole of C7H16 = 7 moles of CO2
= 7 x 44 = 308g

Question 5

Zinc Carbonate = Zinc Oxide + Carbon Dioxide

If 2g of zinc carbonate makes 1.3g of zinc oxide, what mass of carbon dioxide is made?

Answer 5

2 - 1.3 = 0.7g of carbon dioxide