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Zinc is a metal - Edexcel - GCSE Chemistry - Question 2 - 2013 - Paper 1
Question 2
Zinc is a metal. Zinc reacts with dilute hydrochloric acid to produce zinc chloride and hydrogen. Edward used this apparatus to investigate the speed of the reacti... show full transcript
Worked Solution & Example Answer:Zinc is a metal - Edexcel - GCSE Chemistry - Question 2 - 2013 - Paper 1
Step 1
Sketch a line on the graph to show the results that Edward should expect to obtain if he carried out the experiment to completion at 30 °C.
Answer
To sketch the line representing the expected results at 30 °C, you should begin by drawing a curve starting from the origin. This curve should demonstrate a slower reaction at 30 °C compared to the 50 °C reaction, indicated by a lower gradient. The curve should eventually level out at the same volume as the curve for 50 °C but should show that it takes longer to reach that final volume. The line should smoothly rise and then plateau, reflecting the slower reaction rate at the cooler temperature.
Step 2
(ii) Explain why zinc powder has a larger surface area compared to larger pieces of zinc, and how this affects reaction rate.
Answer
Zinc powder has a larger surface area because it is composed of many small particles, which provides more area for collisions with the dilute hydrochloric acid molecules. As a result, there are more (frequent) collisions between the acid and the zinc particles, leading to more successful reactions and a faster reaction rate.
Step 3
(iv) Explain in terms of energy changes what happens during the reaction.
Answer
The reaction involves breaking bonds, which requires heat energy (an endothermic process). Conversely, when new bonds are formed, heat energy is released (an exothermic process). Overall, there is typically a net change where more heat energy is consumed than is released, indicating that energy is given out when the overall reaction is exothermic.
Step 4
(b) Describe how an increase in temperature affects the reaction.
Answer
An increase in temperature makes the reaction go faster by increasing the kinetic energy of the particles involved. This results in a higher frequency of effective collisions, thus increasing the rate at which the reaction occurs.