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, which occurs when an acid reacts with a base to produce salt and water.

A catalyst is a substance that increases the rate of a chemical reaction without being consumed or permanently changed by the reaction itself. It works by lowering the activation energy required for the reaction to proceed.

The results show that smaller pieces of calcium carbonate produce a larger volume of carbon dioxide in a given time. This indicates that smaller pieces have a larger surface area, which allows for more efficient contact with the acid, leading to a faster reaction rate.

To demonstrate the effect of hydrochloric acid concentration on the reaction rate, you would prepare solutions of varying concentrations of hydrochloric acid. Measure equal lengths of magnesium ribbon and place them into separate beakers containing equal volumes of the different acid concentrations. Observe and measure the time taken for visible bubbles to form and the amount of gas produced. The reaction will proceed faster with higher concentration acid, as the frequency of collisions between acid particles and magnesium increases.