Rates

One sample question with the full working. 1 more in the app, with instant feedback and repair sessions for the traps below.

A catalyst

Ais used up in the reaction
Bspeeds up a reaction without being used up
Calways slows a reaction
Dchanges the products

Show the answer and working

Answer: B

Speeds, not used up.

Trap A Thinks a catalyst shifts equilibrium, adds energy or is used up: A catalyst gives an alternative route with lower activation energy for BOTH directions. It is unchanged at the end, so it changes the rate only: never the yield, ΔH or Kc.

Trap C Reverses a trend, direction or effect: State the rule with its direction before looking at the options (down group 1 reactivity INCREASES; exothermic forward reaction: heating shifts LEFT). An option that is the mirror image of the rule is the trap.

Trap D Over-generalises a rule beyond where it holds: Every rule in chemistry has conditions. Before applying one, check the conditions in the stem (electrode type, concentration, moles of gas on each side, metal position).

Traps in Rates

Thinks a catalyst shifts equilibrium, adds energy or is used up
A catalyst gives an alternative route with lower activation energy for BOTH directions. It is unchanged at the end, so it changes the rate only: never the yield, ΔH or Kc.
Reverses a trend, direction or effect
State the rule with its direction before looking at the options (down group 1 reactivity INCREASES; exothermic forward reaction: heating shifts LEFT). An option that is the mirror image of the rule is the trap.
Over-generalises a rule beyond where it holds
Every rule in chemistry has conditions. Before applying one, check the conditions in the stem (electrode type, concentration, moles of gas on each side, metal position).

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