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Difficult Chem Multiple Choice Questions

Hi,

Could you please help me out with these questions, have asked my teachers for help but to no avail. Thanks

8 The gaseous first order reaction, A o B + C, was found to have a half-life of 20*s
when the initial pressure of A was 2 atm.
When the initial pressure of A is increased to 4 atm, the half-life is
A 10 s
B 20 s
C 40 s
D 400 s
(Total for Question 8 = 1 mark)

Spoiler

9 The equation for the equilibrium between nitrogen and oxygen may be written in two ways.
N2 (g) + O2 (g) = 2NO(g) Equilibrium constant K1
½N2(g) + ½O2 (g) U NO(g) Equilibrium constant K2
The standard enthalpy change, H for the reaction as shown in the first equation is +180 kJ mol–1.
(a) What is the standard enthalpy change for the reaction as shown in the second equation?
A +45 kJ mol–1
B +90 kJ mol–1
C +180 kJ mol–1
D +360 kJ mol–1

Spoiler

(d)Find pH of The mixture formed when 25 cm3 of 2 mol dm–3 sodium hydroxide solution is added to 50 cm3 of 2 mol dm–3 ethanoic acid, for which Ka = 1.7 × 10–5 mol dm–3.
A 2.2
B 2.5
C 4.5
D 4.8

Spoiler

Calcium carbonate decomposes at high temperature to form calcium oxide and
carbon dioxide:
CaCO3(s) CaO(s) + CO2(g)
Calcium carbonate is thermodynamically stable at room temperature because for this reaction
A the activation energy is high.
B the enthalpy change, H, is positive.
C entropy change of the system (Ssystem) is positive.
D entropy change of the system (Ssystem) is negative.

Spoiler

20) The hydride ion H- is a strong reducing agent, a good nucleophile and a strong base. Which of the following changes could NOT be bought about by the ion.

A)CH3CHO to CH3CH2OH
B) C2H5BR to C2H6
C) CH2=CH2 to C2H6
D) CH3COOH to CH3COO-

Spoiler

http://www.thestudentroom.co.uk/attachment.php?attachmentid=407637&stc=1&d=1432550656
Answer is

Spoiler

http://www.thestudentroom.co.uk/attachment.php?attachmentid=407639&stc=1&d=1432550772

Spoiler

bump? anyone?