What number of moles of HCl gas will be formed when 22.4 L of H₂ is mixed with 11.2 L of Cl₂ at STP?

1.	1 moles of HCl (g)	2.	2 moles of HCl (g)
3.	0.5 moles of HCl (g)	4.	1.5 moles of HCl (g)

Calculate the number of moles of oxygen (O) atoms in 126 amu of HNO₃. 

1.  2

2.  $\frac{2}{{\mathrm{N}}_{\mathrm{A}}}$

3.  6

4.  $\frac{6}{{\mathrm{N}}_{\mathrm{A}}}$

A 10 g silver coin is completely dissolved in excess concentrated HNO₃ and produces 8.5 g of AgNO₃. Given that the molar mass of silver is 108 g mol⁻¹, what is the percentage purity of silver in the coin?

Calculate the mass percentages of sodium (Na), sulfur (S), and oxygen (O), respectively, in sodium sulphate (Na₂SO₄):

1. 32.4%, 45.05% and 22.6%

2. 22.6%, 45.05% and 32.4%

3. 32.4%, 22.6% and 45.05%

4. 45.05%, 32.4% and 22.6%

Find the amount of copper (in grams) that can be obtained from 100 g of anhydrous copper sulphate (CuSO₄).

1. Fe₃O₂

2. Fe₂O₃

3. Fe₂O₂

4. Fe₃O₄

Find the concentration of sugar, C₁₂H₂₂O₁₁, in mol L⁻¹ when 20 g of sugar is dissolved in enough water to make 2 L of solution.

1. 0.29 mol/L

2. 0.029 mol/L

3. 0.35 mol/L

4. 0.032 mol/L