### Expt – To find the rate of reaction by measuring gas produced

Introduction

This experiment combines observing the effect of reacting an acid with a carbonate (specifically calcium carbonate) with measuring how fast a reaction occurs. Reaction rates are found by measuring a change in a quantity (e.g. mass of solid, volume of gas) over time. In this experiment the volume of carbon dioxide gas evolved will be measured over time.

Method

The glassware needed for this experiment is shown below: Firstly, measure out approximately 0.4 g of calcium carbonate into a weighing bottle. Note carefully the mass of the bottle with and without solid in the table below:

 Mass of empty weighing bottle = Mass of bottle + solid = Mass of bottle – solid = Mass of solid added =

Assemble the apparatus as in the diagram and add 25 cm3 of the hydrochloric acid provided to the side-arm conical flask. Then, once you are ready to start the reaction, quickly add the solid from the weighing bottle to the conical flask, place the bung in the top of the flask and start a stop-watch.

Record the volume of gas produced every 10 seconds in a suitable table until the reaction stops (i.e. no more gas is produced).

Weigh the bottle one last time after the solid is tipped into the flask so that the precise mass of calcium carbonate added can be worked out.

Questions

1. Plot a graph of volume of gas produced (y-axis) vs time (x-axis) and draw a smooth line through the points.

2. Draw a tangent to the smooth line you have drawn at 0 seconds and find the gradient of that line. This is the value of the initial rate of reaction.