W3 Sep S3 Pure Chem EOY Revision 2: Atomic structure & KPT

A substance was heated until it melted, and allowed to cool. The temperature time graph of the substance during the cooling process was recorded as shown below.

Which statement is correct?

• Along PQ, the molecules lose kinetic energy.

• Along QR, the average distance between the molecules is unchanged.

• Along QR, the molecules gain kinetic energy.

• The average distance between the molecules is smaller at PQ than at RS.

The picture below shows the arrangement of particles in hexane at two different temperatures. Hexane has a melting point of -95 ^oC and a boiling point of 70 ^oC.

What could the values of X and Y be?

• X = -100 ^oC, Y = 90 ^oC

• X = -50 ^oC, Y = 10 ^oC

• X = 0 ^oC, Y = 100 ^oC

• X = 10 ^oC, Y = -50 ^oC

Element A has 7 protons. Element B has 8 more protons than A. 

If both elements are found within the first 3 periods of the Periodic Table, which statement about element B is not correct?

• B has more electron shells than A.

• B has the same number of valence electrons as A.

• B and A are found in the same group of the Periodic Table.

• B and A are found in the same period of the Periodic Table.

A stable molecule containing atoms of the elements J, K, L and M has the structure as shown below.

What is the possible identity of elements K and L?

• K: oxygen, L: silicon

• K: fluorine, L: carbon

• K: nitrogen, L: carbon

• K: nitrogen, L: sodium

The diagram shows the electronic structure with only the outer shells of a molecule of a compound XY₂.

What could elements X and Y be?

• chlorine and sulfur

• hydrogen and oxygen

• iodine and nitrogen

• oxygen and neon