Gaps

Question 1

How do you calculate bond energy change?

Answer 1

Reactants (energy in) - Products (energy out)

Question 2

State 3 things that are different about Mendeleev’s periodic table compared to the modern day one

Answer 2

• Mendeleev’s has only atomic mass and not atomic number

• Mendeleev’s has no group 8/ 0

• Mendeleev’s has gaps for undiscovered elements

Question 3

What is meant by Avagadro’s constant?

Answer 3

The number of entities in 1 mole

Question 4

How do you calculate number of molecules?

Answer 4

Avagadro’s constant x Number of moles

Question 5

What happens during the electrolysis of copper(II) sulphate using copper electrodes?

Answer 5

At the cathode (-) Cu²⁺ ions from the solution gain electrons (reduction) and deposit as solid, pure copper on the cathode. The cathode increases in size as copper is deposited.

At the anode (+) Copper metal loses electrons (oxidation) and dissolves into the solution as Cu²⁺ ions. (any impurities fall the bottom of the container) The anode decreases in size as copper dissolves into the solution.

This process is used for purifying copper

Question 5

Why are platinum and graphite electrodes similar?

Answer 5

Because they are both inert and do not react with the solution during electrolysis.

Question 6

How do you calculate the mass of one atom?

Answer 6

Mass number / Avagadro’s constant