June 2020 Paper 1

Question 1

Why would the enthalpy of hydration of one (a) be less exothermic than ion (b)?

Answer 1

-the size of ion b, the less exothermic one, is larger
-so the attraction between the ion and H20 increases

Question 2

What is the equation for enthalpy of hydration, solution and lattice of formation?

Answer 2

-enthalpy of solution = lattice - hydration

Question 3

Why is it necessary to ionise isotopes of an element before they can be analysed?

Answer 3

-so they can be accelerated
-so a current can flow when they hit the detector

Question 4

What is observed when aqueous chlorine is added to sodium bromide solution?

Answer 4

-a yellow solution

Question 5

What is the ionic equation for when aqueous chlorine is added to sodium bromide solution?

Answer 5

-Cl2 + 2Br- >2Cl- + Br2

Question 6

When calculating entropy, do you also account for the number of molecules?

Answer 6

-yes e.g. entropy of 3H2, H2 = 131 so x3 = 393

Question 7

On a Gibbs free-energy graph, what does the gradient represent?

Answer 7

• -delta S / -entropy

Question 8

On a Gibbs free-energy graph, what does the y intercept represent?

Answer 8

-delta H

Question 9

What can be done to maintain the EMF of a fuel cell when in use?

Answer 9

-constantly add reactants