Cambridge OCR GCSE (9-1) · Gateway Science - Chemistry A - J248
3 multiple-choice questions marked as you go, and 3 written questions with worked solutions. All on Introducing chemical reactions.
A student reacts a piece of calcium carbonate with dilute hydrochloric acid in an open conical flask placed on a digital balance. During the reaction, the reading on the balance decreases. Which statement explains this observation in terms of the law of conservation of mass?
Calculate the volume occupied by 0.88 g of carbon dioxide gas (\(CO_2\)) at room temperature and pressure (RTP).
(Relative atomic masses: \(C = 12, O = 16\); Molar volume of gas at RTP = \(24\text{ dm}^3\text{/mol}\))
A chemist reacts 4.0 g of calcium with 4.0 g of oxygen to produce calcium oxide:
\(2Ca + O_2 \rightarrow 2CaO\)
Which reactant is the limiting reactant? (Relative atomic masses: \(Ca = 40, O = 16\))
Identify the correct state symbol for a substance that is dissolved in water to form a solution.
Write your answer out first, then check it against the worked solution.
A student reacts \(5.00\text{ g}\) of calcium carbonate with excess hydrochloric acid in an open beaker. The final mass of the beaker and its contents is found to be less than the initial mass. Explain this observation using the particle model.
Write your answer out first, then check it against the worked solution.
Balance the following chemical equation and determine the stoichiometry (ratio of moles) between the alkali and the acid:
\(NaOH(aq) + H_2SO_4(aq) \rightarrow Na_2SO_4(aq) + H_2O(l)\)
Write your answer out first, then check it against the worked solution.
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