Measuring rates of reactionIB MYP Chemistry: Mind map

Exam questions on Measuring rates of reaction

1. A student in Cape Town reacts magnesium ribbon with excess dilute hydrochloric acid in a conical flask connected to a gas syringe. She records the volume of hydrogen collected at regular intervals and plots volume against time.
   Between 0 and 20 s she collects 30 cm³ of gas, and between 60 s and 80 s she collects 6 cm³. Calculate the mean rate of reaction, in cm³ s⁻¹, for each period.2 marks
2. A technician in Manchester places a conical flask containing marble chips and dilute hydrochloric acid on a top-pan balance. A loose plug of cotton wool is fitted in the neck of the flask, and the balance reading is recorded every 30 seconds as the reaction proceeds.
   The first reading is 152.40 g and the reading after 60 seconds is 151.92 g. Calculate the mean rate of mass loss, in g s⁻¹, over the first 60 seconds.2 marks
3. In a school in Mumbai, a student mixes sodium thiosulfate solution with dilute hydrochloric acid in a flask standing on a cross drawn on paper. A yellow solid forms and makes the mixture cloudy. The student times how long it takes until the cross can no longer be seen when looking down through the mixture.
   Explain how the time taken for the cross to disappear can be used to compare the rates of reaction in different experiments.3 marks