1. What amount of oxygen, O₂, (in moles) contains 1.8 ×10²² molecules?

2. Separate 20.0 cm³ solutions of a weak acid and a strong acid of the same concentration are titrated with NaOH solution. Which will be the same for these two titrations?

I.       Initial pH

II.      pH at equivalence point

III.     Volume of NaOH required to reach the equivalence point

3. Which compound has the empirical formula with the greatest mass?

4. 3.0 dm³ of sulfur dioxide is reacted with 2.0 dm³ of oxygen according to the equation below.

2SO₂(g) +O₂(g) → 2SO₃(g)

          What volume of sulfur trioxide (in dm³)is formed? (Assume the reaction goes to completion and all gases are measured at the same temperature and pressure.)

5. Lithium hydroxide reacts with carbon dioxide as follows.

2LiOH + CO₂ → Li₂ CO₃ +H₂O

          What mass (in grams) of lithium hydroxide is needed to react with 11 g of carbon dioxide?

6. Which solution contains the smallest amount of H+ ions?

7. The lattice enthalpy values for lithium fluoride and calcium fluoride are shown below.

         LiF(s)       ∆H^ï = +1022 kJ mol⁻¹ 
       CaF₂(s)     ∆H^ï = +2602 kJ mol⁻¹

          Which of the following statements help(s) to explain why the value for lithium fluoride is less than that for calcium fluoride?

I.       The ionic radius of lithium is less than that of calcium.

II.      The ionic charge of lithium is less than that of calcium.

8. What is the mass of one mole of carbon-12?

9. How many hydrogen atoms are contained in one mole of ethanol, C₂H₅OH?

10. The percentage by mass of the elements in a compound is

C = 72%,    H = 12 %,    O = 16%.

          What is the mole ratio of C : H in the empirical formula of this compound?