Electrochemistry and periodic trends

Written by Dr. Ayesha Nadeem (Chemistry)

ECAT · Chemistry · 6 questions

Name: ____________________ Date: ____________

How much charge is needed to deposit 1 mole of copper from Cu2+ ions?
- A 0.5 faraday
- B 1 faraday
- C 3 faradays
- D 2 faradays
In the Daniell cell (Zn and Cu), the anode is:
- A Zinc
- B Copper
- C Carbon
- D The salt bridge
Which has the lower first ionisation energy, beryllium or boron?
- A Beryllium
- B Boron
- C They are equal
- D Neither has an ionisation energy
Which of these metals reacts most vigorously with water?
- A Calcium
- B Lithium
- C Potassium
- D Magnesium
What is the oxidation state of chromium in K2Cr2O7?
- A +7
- B +3
- C +6
- D +2
Which gas is given off when zinc reacts with dilute hydrochloric acid?
- A Chlorine
- B Hydrogen
- C Carbon dioxide
- D Oxygen

Answer key

1. D, 2. A, 3. B, 4. C, 5. C, 6. B

Each Cu2+ ion needs two electrons, so one mole needs two moles of electrons, which is 2 faradays.
Zinc is oxidised, so it is the anode. Copper ions are reduced at the copper cathode.
Boron's outer electron is in a 2p orbital, which is higher in energy and easier to remove than a 2s electron of beryllium.
Reactivity increases down Group 1 and potassium is below lithium. It is also more reactive than Group 2 metals in the list.
Two K are +2 and seven O are -14. The two Cr must supply +12, so each is +6.
Zinc displaces hydrogen from the acid, giving zinc chloride and hydrogen gas.