Mock

Question 1

3.2. The C–F bond is polar. Explain why CF4 is a non-polar molecule. (2)

Answer 1

(1) the molecule is symmetrical
(2) so the dipoles cancel out

Question 2

5.2. In TOF mass spectrometry, why must the atoms be ionised? (1)

Answer 2

so that they can be accelerated (by an electric field)

Question 3

5.3. Explain why 208Pb+ has a longer time of flight than 206Pb+. (2)

Answer 3

(1) same KE
(2) lower velocity/speed

Question 4

7.2. Why is ice less dense than liquid water at 0 degrees? (1)

Answer 4

water molecules are held further apart

Question 5

1.1. Gallium is a metal. Describe the bonding in solid Gallium. (2)

Answer 5

(1) attraction between positive ions
(2) and delocalised electrons