OCR Chemistry Paper 1 Questions with
Correct Answers
rate of reaction - ANSWERSChange in concentration of a reactant of product per unit
time
order - ANSWERSThe power in which the concentration of the reactant is raised in the
rate equation
half-Life - ANSWERSThe time taken for the concentration of a reactant to reduce by
half
rate determining step - ANSWERSThe slowest step in a reaction mechanism of a multi-
step reaction
how would you carry out a clock reaction? - ANSWERS- measure time taken from the
start of reaction until there is a visible change.
- initial rate = 1/T
- carry out a series of clock reactions, varying each reactant
- plot graph of initial rate against initial concentration for each reactant
what is the effect of temperature on a rate constant and rate of reaction? - ANSWERS-
raising the temperature speeds up most reactions by increasing the rate constant, k.
- for most reactions, every 10C will double the rate -> this reflects the greater number of
reacting particles that exceed the activation energy
what is the effect of temperature on the value of Kc in exothermic and endothermic
reactions? - ANSWERS• if the forward reaction is endothermic as the temperature
increases, Kc increases. The equilibrium yield on the right increases, and decreases on
the left.
• if the forward reaction is exothermic as the temperature increases, Kc decreases. the
equilibrium yield on the left increases, and decreases on the right.
what is the effect of concentration and pressure on Kc? - ANSWERS• unaffected by
changes in concentration and pressure.
, what is an acid? - ANSWERS• a species which donates a proton.
what is a base? - ANSWERS• a species that accepts a proton.
what is the three types of acids? hence state how many proton's these acids release -
ANSWERS• monobasic - each molecule may release 1 proton.
• dibasic - each molecule may release 2 proton's.
• tribasic - each molecule may release 3 proton's.
provide the general formula for an acid-carbonate reaction - ANSWERS• acid +
carbonate = salt + carbon dioxide + water
provide the general formula for an acid-base reaction - ANSWERS• acid + base = salt +
h2o
provide the general formula for an acid-metal reaction - ANSWERS• acid + metal = salt
+ h2
what is an acid-base pair? - ANSWERS• a pair of two species that transform into each
other by gain or loss of a proton.
what does a large Ka value indicate? - ANSWERS• a lot of dissociation, a strong acid.
what does a small Ka value indicate? - ANSWERS• a small amount of dissociation, a
weak acid.
what is the formula for the ionic product of water? - ANSWERS• Kw = [H+][OH-]
how would you calculate the pH of weak monobasic acids? - ANSWERS• Ka =
[H+]^2/[HA]
what is a buffer solution? - ANSWERS• a system that minimises pH changes in addition
of small amounts of an acid or a base.
provide 2 methods to prepare a buffer solution - ANSWERS• a weak acid and the salt of
the weak acid,
• a weak base and its chloride.
what occurs to a buffer solution, upon addition of an acid? - ANSWERS• [H+] increases,
• Conjugate base reacts with H+,
• shifts equilibrium to the left,
• this minimises H+ ions.
what occurs to a buffer solution, upon addition of an alkali? - ANSWERS• [OH-]
increases.
• H+ ions react with OH- ions,
Correct Answers
rate of reaction - ANSWERSChange in concentration of a reactant of product per unit
time
order - ANSWERSThe power in which the concentration of the reactant is raised in the
rate equation
half-Life - ANSWERSThe time taken for the concentration of a reactant to reduce by
half
rate determining step - ANSWERSThe slowest step in a reaction mechanism of a multi-
step reaction
how would you carry out a clock reaction? - ANSWERS- measure time taken from the
start of reaction until there is a visible change.
- initial rate = 1/T
- carry out a series of clock reactions, varying each reactant
- plot graph of initial rate against initial concentration for each reactant
what is the effect of temperature on a rate constant and rate of reaction? - ANSWERS-
raising the temperature speeds up most reactions by increasing the rate constant, k.
- for most reactions, every 10C will double the rate -> this reflects the greater number of
reacting particles that exceed the activation energy
what is the effect of temperature on the value of Kc in exothermic and endothermic
reactions? - ANSWERS• if the forward reaction is endothermic as the temperature
increases, Kc increases. The equilibrium yield on the right increases, and decreases on
the left.
• if the forward reaction is exothermic as the temperature increases, Kc decreases. the
equilibrium yield on the left increases, and decreases on the right.
what is the effect of concentration and pressure on Kc? - ANSWERS• unaffected by
changes in concentration and pressure.
, what is an acid? - ANSWERS• a species which donates a proton.
what is a base? - ANSWERS• a species that accepts a proton.
what is the three types of acids? hence state how many proton's these acids release -
ANSWERS• monobasic - each molecule may release 1 proton.
• dibasic - each molecule may release 2 proton's.
• tribasic - each molecule may release 3 proton's.
provide the general formula for an acid-carbonate reaction - ANSWERS• acid +
carbonate = salt + carbon dioxide + water
provide the general formula for an acid-base reaction - ANSWERS• acid + base = salt +
h2o
provide the general formula for an acid-metal reaction - ANSWERS• acid + metal = salt
+ h2
what is an acid-base pair? - ANSWERS• a pair of two species that transform into each
other by gain or loss of a proton.
what does a large Ka value indicate? - ANSWERS• a lot of dissociation, a strong acid.
what does a small Ka value indicate? - ANSWERS• a small amount of dissociation, a
weak acid.
what is the formula for the ionic product of water? - ANSWERS• Kw = [H+][OH-]
how would you calculate the pH of weak monobasic acids? - ANSWERS• Ka =
[H+]^2/[HA]
what is a buffer solution? - ANSWERS• a system that minimises pH changes in addition
of small amounts of an acid or a base.
provide 2 methods to prepare a buffer solution - ANSWERS• a weak acid and the salt of
the weak acid,
• a weak base and its chloride.
what occurs to a buffer solution, upon addition of an acid? - ANSWERS• [H+] increases,
• Conjugate base reacts with H+,
• shifts equilibrium to the left,
• this minimises H+ ions.
what occurs to a buffer solution, upon addition of an alkali? - ANSWERS• [OH-]
increases.
• H+ ions react with OH- ions,
