Pages in this set

Page 1

Preview of page 1
2.1 TEST MARK SCHEME

1. (a)

Enthalpy (Energy) to break a (covalent) bond (1) OR dissociation
energy
Varies between compounds so average value used (1) QL mark
OR average of dissociation energies in a single molecule / e.g.
CH4
Do not allow mention of energy to form bonds
but with…

Page 2

Preview of page 2
= +146 ­ 496/2 (or 2 × 463 + 146 ­(2 × 463 + 496/2)

1
= ­ 102 (kJ mol­1) (1)
1
(accept no units, wrong units loses a mark
+102 scores (1) only)

(b) C(s) + 2H2(g) CH4(g) equation (1) Correct state symbols (1)

2

(c) (i)

Macromolecular…

Page 3

Preview of page 3
(b) (i)

C2H6 + 3½O2 2CO2 + 3H2O (1)
(ii) H = 2 × H (CO2) + 3 × H (H2O) ­ H (C2H6) (1)
= ­ 788 ­ 858 ­ (­85)
= ­ 1561 kJ mol­1
(1) (1)



4

[6]


4. (b)

H = Hc (reactants) ­ Hc (products)…

Page 4

Preview of page 4
3
ignore units even if wrong
Allow 1/3 for +773
[9]


5. (a)

(i)

enthalpy (or heat or heat energy) change when

3
1 mol of a substance (1) (QL mark) is formed from its elements (1)
all substances in their standard states (1) (or normal states at 298K,
100…

Page 5

Preview of page 5
value (1)
sign (1) this mark can be given despite CE
for /2

Note various combinations of answers to part (c) score as follows:
­89 to ­91 kJ (8) (or ­89000 to 91000J)
no units (7)
+89 to +91 kJ (7) (or + 89000 to +91000J)
no units (6)
­44…

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all resources »