Advanced level 2025 North West regional mock Chemistry guide

Advanced level 2025 North West regional mock Chemistry guide

Advanced level 2025 North West regional mock Chemistry guide

SECTION A: PHYSICAL AND GENERAL CHEMISTRY
1. (a)
(i) A molecule is a group of two or more atoms
chemically bonded together. (1 mk)
(ii)Mass number (A) is the total number of protons
and neutrons found in an atomic nucleus(1 mk)
(b) Number of protons = 27
Number of Neutrons = 59 – 27 = 32
(2 x ½ = 1 mk)
(c)
(i) When an electron occupies the lowest possible
energy level in an atom (n = 1 level). (1 mk)
(ii) When an electron absorbs energy and moves to a
higher energy level than its ground state (n = 2
or higher). (1 mk)
(d)

(4 x ½ = 2 mks)
(e)
(i) – An acid is a proton donor (1 mk)
– A conjugate base is the species that remains after
an acid donates a proton to a base. (1 mk)
(ii)
pH = – log[H+] ⇒ 10.6 = – log[ H+] ⇒ [H+]
= 2.51 x 10-11(𝟏 𝐦𝐤)
[H+][OH–] = Kw ⇒ [OH–] = Kw
[H+]
=
1.0 x 10-14
2.51 x 10-11 (𝟏 𝐦𝐤)
[OH–] = 3.98 x 10-4(𝟏 𝐦𝐤)
Alternative
pH + pOH = 14 ⇒ pOH = 14 – pH
But PH = 10.6 ⇒ pOH = 14 – 10.6 = 3.4
POH = – log[OH–] ⇒ log[OH–] = -3.4
⇒ [OH–] = 10-3.4
[OH–] = 3.98 x 10-4
(f)
(i) The enthalpy of atomization is the heat absorbed
when 1 mol of a gaseous atom is formed from the
element in its standard state. (1 mk) e.g.
Na(s) ⟶ Na(g)(1 mk)
(ii)The standard lattice energy is the enthalpy change
when 1 mol of an ionic compound is formed from
its gaseous ions under standard conditions. (1 mk)
e.g.
Na
(g)
+
+ Cl
(g)
–
⟶ NaCl(s)(1 mk) Anyone
Mg( 2g+) + O( 2g-) ⟶ MgO(s)
(g)
(i) The average rate of a reaction is the change in the
concentration of a reactant or product per unit
time. (1 mk)
(ii) Average rate = Change in concentration
Change in time =
(1-0.03) 𝑚𝑜𝑙𝑑𝑚-3
1 x 60 x 60 s
(𝟏 𝐦𝐤)
=
0.97 moldm-3
3600 s
= 2.69 x 10-4moldm-3s-1(𝟏 𝐦𝐤)
(iii)
(Total = 20 marks)