During a synthesis experiment, a chemist prepares a sample of sulfur dioxide gas, SO2SO_2SO2, which is significantly denser than air. The gas is collected in an upright, open-topped gas cylinder by downward delivery.
To determine when the cylinder is full of the acidic gas, a strip of damp blue litmus paper is positioned at the top rim of the cylinder.
Explain the chemistry and physical reasoning behind using litmus paper that is damp and placing it specifically at the top rim of the cylinder.
Practise Edexcel GCSE Chemistry Acids with exam-style questions for Foundation and Higher tier. 100 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.