During an investigation into the effect of temperature on the rate of reaction between sodium thiosulfate and hydrochloric acid, a student measures the time taken for a black cross marked under the reaction flask to become obscured by the precipitate of sulfur.
State the piece of apparatus that should be used to measure this time.
Practise Edexcel GCSE Chemistry Rates of reaction with exam-style questions for Foundation and Higher tier. 166 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
