Moles Revision

1)        What is the mass, in g, of:-

a)        2 moles of carbon, C

b)        0.25 moles of magnesium, Mg

c)        3 moles of sodium hydroxide, NaOH

d)        0.5 moles of sulphuric acid, H₂SO₄

2)        Convert the following masses into moles:-

a)        13g of lithium fluoride, LiF

b)        72g of water, H₂O

c)        0.44g of carbon dioxide, CO₂

3)        What is the mass in g of:-

a)    5 moles of hydrogen atoms, H

b)    5 moles of hydrogen molecules, H₂

Questions 4 - 6. Hint - a mole of anything contains the same number of particles; so when you have amounts expressed as moles it is equivalent to counting particles.

4)    Which one has the greatest number of atoms?

A 22g of boron, B                 B 12 g of carbon, C

C 21 g of lithium, Li              D 80 g of calcium, Ca

5)    Which one of the following contains the greatest number of molecules?

A 36g of water, H₂O

B 64g of sulphur dioxide, SO₂

C 60g of hydrogen fluoride, HF

D 32g of methane, CH₄                                   

6)    Which of the choices in Question 5 contains the greatest number of atoms?

Questions 7 - 10.  Gas volumes can also be used to measure moles. One mole of any gas has a volume of 24 litres at room temperature and pressure (rtp).

7)    How many moles is 6 litres of carbon dioxide at rtp?

8)    What is the volume of 3 moles of hydrogen at rtp?

9)    What is the mass of 2.4 litres of oxygen,O, at rtp?

10) What volume is 6 grams of hydrogen, H, at rtp?

Questions 11 - 14. Assume that the Avogadro number is approximately 6 x 10²³

11) Approximately how many molecules are there in 3 g of water, H₂O?

12)  Approximately how many atoms are there in 3 g of water?

13) In 12 litres of ammonia gas, NH₃ at rtp

a)      approximately how many molecules are there?

b)      approximately how many atoms are there?

14)  What is the total number of ions in one mole of magnesium bromide, MgBr₂?

15) How many moles of ions in total are there in one mole of MgBr₂?