C1 PP1

Question 1

Suggest one reason why nitrogen dioxide is not formed by this reaction in an internal combustion engine

Answer 1

Temperature exceeds this value

Question 2

Write an equation to show how nitrogen monoxide is formed in an internal combustion engine

Answer 2

N2 + O2 -> NO

Question 3

Explain why the free energy change for the reaction to form nitrogen monoxide stays approx constant at diff temps

Answer 3

No change in number of moles so entropy stays constant

Question 4

Explain why ammonia is very soluble in water

Answer 4

Hydrogen bonding between NH3 and H2O

Question 5

Write

Question 6

An equation for the reaction of ammonia with water

Answer 6

NH3 + H2O <–> NH4+ + OH-

Question 7

Explain why the pH of a solution containing 1.0 moldm-3 of ammonia is less than 14 at 298K

Answer 7

Incomplete reaction
Weak base

Question 8

What does buffer mean

Answer 8

Solution which resists change in pH when small amount of acid added

Question 9

State why calibrating a pH meter just before it is used improves the accuracy of the pH measurement

Answer 9

Over time meter does not give accurate readings

Question 10

Describe how you would obtain the pH curve for the titration

Answer 10

Measure inital pH
Add alkali in known small portions
Stir mixture
Measure pH
Repeat until alkali in excess
Add in smaller increments near endpoint

Question 11

Briefly outline how you would carry out an experiment to confirm your answer to part b

Answer 11

Allow cell to discharge until [Cu2+] is 0.5
Confirmed by colourimetric measurement
Weigh Zn electrode before and after experiment