Chemistry
Daily Exam Challenge: Chemistry (Higher)
Instructions
- • Use black ink or black ball-point pen. Draw diagrams in pencil.
- • Answer all questions in the spaces provided.
- • Do all rough work in this question paper. Cross through any work you do not want to be marked.
- • Show all your working out — marks may be awarded for correct working even if the answer is wrong.
Information
- • The total mark for this paper is 20.
- • The marks for each question are shown in brackets — use this as a guide as to how much time to spend on each question.
- • Questions labelled with an asterisk (*) are where the quality of your written communication will be assessed.
Answer all questions in the spaces provided.
A student carries out a titration to find the concentration of a solution of sulfuric acid (H₂SO₄). 25.0 cm³ of 0.200 mol/dm³ NaOH is neutralised by 12.5 cm³ of H₂SO₄. 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O (a) Calculate the number of moles of NaOH used. (b) Calculate the number of moles of H₂SO₄ that reacted. (c) Calculate the concentration of the H₂SO₄ in mol/dm³. (d) Calculate the concentration of the H₂SO₄ in g/dm³.
Explain why the melting point of sodium chloride (801°C) is much higher than that of silicon dioxide which has a similar structure? Actually, silicon dioxide melts at 1713°C. Explain why SiO₂ has a higher melting point than NaCl, even though both have giant structures.
Iron can be extracted from iron oxide using carbon monoxide: Fe₂O₃ + 3CO → 2Fe + 3CO₂ (a) Identify what is oxidised and what is reduced. Explain your answer. (b) 500 tonnes of iron ore contains 70% Fe₂O₃ by mass. Calculate the maximum mass of iron that could be extracted.
End of Questions
Total marks: 20