Experiments to measure the rate of reaction
4 marks · NormalDescribe how the surface area of marble chips could be changed in an experiment investigating the rate of reaction between calcium carbonate and hydrochloric acid.
Explain, using particle collision theory, why the reaction rate changes when marble chips are powdered instead of used whole.
State one variable, other than surface area, that should be kept constant during this investigation.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) By using marble chips in two different forms: as large lumps or as powder. · must show Describes using large or small/powdered marble chips
(b) Powdered marble chips have a greater surface area exposed to the acid, so more particles are available to react at once. This increases the frequency of successful collisions between particles, leading to a faster reaction. · must show surface area increases, frequency of successful collisions increases, faster reaction
(c) Temperature (or concentration of acid, or volume of acid, or mass of marble used). · must show Names any valid controlled variable
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Describes a valid way to change marble chip surface area (e.g., using powder or larger pieces).
M1 (b) · 1 mark · Mentions increase in surface area exposes more particles.
M2 (b) · 1 mark · States this increases the frequency of successful collisions, explaining faster reaction.
B2 (c) · 1 mark · States a valid variable to keep constant (e.g., temperature, acid concentration, volume of acid, or mass of marble).
Worked solution
a) Change the surface area by using marble chips as large lumps, as small pieces, or as powder. b) Powdered marble chips have a greater surface area, exposing more particles to the acid. This increases the frequency of collisions, so the reaction is faster according to collision theory. c) The concentration or volume of acid, the temperature, or the mass of marble used should be kept constant.