Gas volume answer 4b

Improved method

The apparatus on the right should get round the problem of the early escaping gas. The septum is a self-sealing rubber cap. The needle of the syringe can be passed through it and the acid injected. When the needle is withdrawn, the septum seals so that no gas can escape through the needle hole. When the 10 cm³ of acid is injected the gas syringe will be forced out by 10 cm³. This needs to be taken into account when measuring the final gas volume.

Analysis and evaluation exercise

0.315 g of the solid carbonate was used. 10 cm³ of 1.0 M hydrochloric acid was injected through the septum. An initial gas volume of 56 cm³ was measured. On shaking the solution further gas was released, giving a final figure of 62 cm³.

Use the results to determine the most likely formula for the unknown carbonate. Carry out an error analysis on the experiment and suggest possible improvements.

Answer