Page 245 - Chemistry

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27. a) ∆H 1 – Lattice energy 1

∆H 2 – Hydrogen energy 1
b) ∆H 3 = ∆H 2 + ∆H 1 1
Reaction rates and reversible reactions
1. colour changes from red to blue
+
-
H 3O ions and L (aq) ions which form red solution.
2. (a) H 4 – latent heat of fusion
(b) H 3 - is negative particles lose hat/process is exothermic/heat is given out (any ) 
3. a) H-H(g) + Cl – Cl (g) 2H – Cl
Bonds broken bonds formed
∣H-H = 435 KJ 2 H – Cl = 430 x 2
∣ Cl – Cl = 240 KJ. = 860 KJ.
Total = 675 KJ.
∆H R = 860 + 675 √ ½

= -185KJ √ ½
b)
Energy
KJ/mol
½
H 2(g) + Cl(g) √
√ ½ ∆H = -185KJ √ ½
2 HCl

√ ½
Reaction path. for both axes
named.
4.

2MHCl
B C

in cm 3 1MHCl
 ½
Volume of Hydrogen

- Graph should be less steeper showing lower reaction rate since HCl is less concentrated. √ ½
Time (secs)
b) Graph flattens out at BC showing that all the magnesium has been used up, hence, no
reaction is taking place √ ½ and there is therefore no evolution of hydrogen gas. √ ½ The
volume of the gas, therefore, remains constant. √ ½

5. a) Pale yellow liquid is observed. √ 1 Backward reaction is favoured since √ ½ it is exothermic.
Dinitrogen tetra oxide liquefies √ ½ at very low temperature to pale yellow liquid.

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