Preventing rusting by galvanising
2 marks · NormalState why rusting is more rapid in salty water than in pure water.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
Salty water increases the rate of rusting because the salt increases electrical conductivity, speeding up the redox reactions involved in rusting.
Also accept: Salt increases conductivity and helps the redox reactions.
Common mistakes: Just says 'salt makes it rust.'
Show mark scheme and worked solution
Marking points
B1 · 1 mark · States salty water increases electrical conductivity.
B2 · 1 mark · Links to faster redox reactions or increased rusting rate.
Worked solution
Salty water is a better conductor of electricity, so the rusting (redox) reactions happen more quickly than in pure water.