exam specific answers (properties of period 3 elements and their oxides)

Question 1

explain why sodium oxide forms an alkaline solution when it reacts with water? (2)

Answer 1

sodium oxide contains O^2- ions
these O^2- react with water forming OH^- ions

Question 2

describe a test you could carry out in a test tube to distinguish between sodium oxide and phosphorus oxide? (3)

Answer 2

react the substances with water
add litmus paper
litmus paper will turn blue with sodium oxide solution and red with phosphorus oxide solution

Question 3

explain why ionic bonding causes some period 3 oxides to have basic properties. (2)

Answer 3

they contain O^2- ions which form water

Question 4

suggest why sulfur dioxide forms a weakly acidic solution (1)

Answer 4

it is only partially ionised in the reaction with water

Question 5

explain why the atomic radius decreases across period 3 from sodium to chlorine. (2)

Answer 5

nuclear charge increases
shielding is similar