1. Practice questions Module 1

2. Basic skills M r and moles to grams Grams and moles to M r M r and grams to moles Concentration and volume to moles Concentration and moles to volume Volume and moles to concentration Read equation, use it to calulate moles Gas equation – derive any one value from the others by changing subject and substituting in.

3. e.g. 1 What will you do? HCl + NaOH  NaCl + H 2 O 500 ml of acid was spilt. 670ml of 1 molar alkali was needed to neutralise it, so what was the concentration of the original acid? Suggested steps: 1.Moles of alkali from volume in dm 3 x concentration 2.Equation shows this equals moles of acid 3.Find concentration from volume and moles 4.If you’re clever you can do it in one go. I don’t.

4. e.g. 2 What will you do? H 2 SO 4 + 2NaOH  Na 2 SO 4 + H 2 O 180 ml of alkali was spilt. 275ml of 0.25 molar acid was needed to neutralise it, so what was the concentration of the original alkali? Suggested steps: 1.Moles of acid from concentration x volume (don’t forget this needs to be in dm 3 ) 2.Equation shows this equals half the moles of alkali so double it 3.Find concentration from volume and moles

5. e.g. 3 What will you do? H 2 SO 4 + Na 2 CO 3  Na 2 SO 4 + H 2 O + CO 2 210g of sodium carbonate was reacted with an excess of 0.5 molar acid. What volume of carbon dioxide was evolved (assume 298K and 101kPa, R=8.31)? Likely steps: 1.Moles of carbonate from mass and M r 2.Equation shows this equals the moles of CO 2 3.Could use 24 litres per mol or use ideal gas equation 4.Change subject of ideal gas equation 5.Use IG equation to find volume of this many moles of gas.

6. e.g. 4 What will you do? H 2 SO 4 + 2NaHCO 3  Na 2 SO 4 + 2H 2 O + 2CO 2 4.90g of sodium hydrogencarbonate was reacted with an excess of acid. What volume of carbon dioxide was evolved? Likely steps: 1.Moles of carbonate from mass and M r 2.Equation shows this equals the moles of CO 2 3.Multiply moles by 24 dm 3 to find volume of this many moles of gas.

7. e.g. 5 What will you do? 2H 2 (g) + O 2 (g)  2H 2 O (g) 1.2 dm 3 of hydrogen was placed in a balloon at 110kPa and 293K and ignited. What mass of water vapour was produced? 1.Moles of hydrogen from ideal gas equation 2.Equation shows this equals the moles of H 2 O 3.Find mass of this many moles of gas.

8. e.g. 6 What will you do? Some sucrose (C 6 H 12 O 6 ) is burnt in a school laboratory. Write a full balanced equation for this C 6 H 12 O 6 (s) + 6O 2 (g)  6H 2 O(g) + 6CO 2 (g) The mass of the sucrose was 14.3g. What volume of carbon dioxide was evolved? 1.Moles of sucrose from mass and M r 2.Equation shows the moles of CO 2 are 6 times this, so multiply by 6 3.Assume normal temperature and pressure – 100kPa, 298K. (or could use 24 litres per mole) 4.Use ideal gas equation to find the volume of this many moles of gas.

9. e.g. 7 What will you do? Some propanol (C 3 H 7 OH) is burnt in a school laboratory. Write a full balanced equation for this 2C 3 H 7 OH (l) + 9O 2 (g)  8H 2 O(g) + 6CO 2 (g) The mass of the propanol was 119g. What mass of carbon dioxide was evolved? 1.Moles of propanol from mass and M r 2.Equation shows the moles of CO 2 are 3 times this, so multiply by 3 3.Find the mass of this many moles of gas.

10. e.g. 8 What will you do?