Random full past papers

Question 1

A student suggested the difference in rates of reaction of strontium and barium with water is due to them having different sums of first and second ionization energies. Discuss (6)

Answer 1

• the sum of the first two ionisation energies for barium is lower
• because barium is a larger atom
• with more shielding (of electrons and shells)
• which outweighs its greater nuclear charge (so it is easier for it to lose its e- and so has lower first and second IEs)
• so barium is more reactive

Question 2

number of ions in 9.53 grams MgCl2

Answer 2

C - 1.81 x 10^23

Question 3

Predict the physical state of astatine at room temperature

Answer 3

solid because the strength of london forces increases

Question 4

relative atomic mass definition

Answer 4

average mass of an atom of an element compared to the mass of an atom of carbon-12

Question 5

Explain why a small peak occurs at m/z 80 when analysing a sample of Br2 with only the 79Br and 81Br isotopes present?

Answer 5

Br2 has a mass of 160

so here a Br2 2+ causes the m/z = 80

Question 6

3 issues + how to fix with apparatus often used in ideal gas equation experiment

Answer 6

1) hydrogen escapes from apparatus
solution - use sealed apparatus with gas syringe

2) large measuring cylinder cannot measure volume accurately
solution - use smaller cylinder

3) magnesium ribbon covered with oxide
solution - clean with abrasive before weighing

Question 7

hydochloric acid and sodium carbonate ionic equation

Answer 7

2H+ + CO3 2- —-> CO2 + H2O

Question 8

explain why S-H and O-H bond lengths are different

Answer 8

• sulfur is a larger atom
• so it has more shielding
• so it has a weaker attraction between its nucleus and BONDING electrons