6 A technician made some dilute sodium hydroxide solution by carefully adding some solid sodium hydroxide to pure water - Edexcel - GCSE Chemistry - Question 6 - 2013 - Paper 1

The reaction between sodium hydroxide and dilute hydrochloric acid is a neutralisation reaction, where an acid and a base react to form a salt and water.

A catalyst is a substance that increases the rate of a reaction without being consumed in the process. It works by lowering the activation energy needed for the reaction to occur, thereby speeding up the reaction.

The results indicate that smaller pieces of calcium carbonate produce a larger volume of carbon dioxide in a given time. This is because smaller pieces have a larger surface area, which leads to a higher reaction rate, allowing for more frequent collisions between reactant particles.

To demonstrate this, you would prepare several solutions of hydrochloric acid at different concentrations. Then, measure equal lengths of magnesium ribbon and add them to each solution in separate containers. Observe the reaction by measuring the volume of hydrogen gas produced or the time taken for the magnesium ribbon to dissolve. As the concentration of hydrochloric acid decreases, the rate of hydrogen gas production should also decrease, demonstrating the effect of concentration on reaction rate.