2021 P1 Q28 - Calculate Increase in Mass of Cathode during Electrolysis

Let's take a look at 2021 A Levels H2 Chemistry Paper 1 Question 28.

2021 p1 q28 question

We are required to determine the increase in mass of cathode.

First let us calculate the number of moles of electrons involved during this electrolysis using Faraday's equations.

2021 p1 q28 calculate mole of electrons

Next we have to deduce the reaction at the cathode.

Since electrolyte is 1.0 moldm-3 of Cu2+ and Ni2+, we have to compare their standard electrode potentials and determine which is more likely reduced at the cathode.

2021 p1 q28 compare E value

Since Cu2+ has a more positive E value, it is more likely reduced than Ni2+.

Therefore Cu2+ will be reduced at the cathode.

2021 p1 q28 reduction of Cuii

Now we can compare mole ratio between copper and electrons to determine moles and mass of copper deposited at the cathode.

2021 p1 q28 calculate mass of Cu deposited

Hence the answer to this question is option C.

2021 p1 q28 answer

Topic: Electrochemistry, Physical Chemistry, A Level Chemistry, Singapore

Back to list of questions for 2021 A Level H2 Chemistry Paper 1.

Found this A Level Chemistry video useful?

Please LIKE this video and SHARE it with your friends!

Join my 10,000+ subscribers on my YouTube Channel for new A Level Chemistry video lessons every week.

Check out other A Level Chemistry Video Lessons here!

Need an experienced tutor to make Chemistry simpler for you?

Do consider signing up for my JC Chemistry Tuition classes at Bishan, weekly LIVE webinars or on-demand video lessons!