WASSCE Chemistry · Paper 1 style

Solutions

One sample question with the full working. 3 more in the app, with instant feedback and repair sessions for the traps below.

The solubility of a salt is 60 g per 100 g of water at 60 °C and 25 g per 100 g at 20 °C. What mass of crystals forms when a saturated solution containing 100 g of water is cooled from 60 °C to 20 °C?

A35 g
B85 g
C60 g
D25 g

Show the answer and working

Answer: A

60 − 25 = 35 g crystallise.

Trap B Uses the wrong arithmetic operation: Write the relationship in words before substituting (crystals = solubility at high T − solubility at low T; neutrons = A − Z; three doublings = 2³). Then check the size of the answer.

Trap C 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).

Trap D Picks a related substance or process with a different role: Learn reagents and processes as one-line 'name → job' cards and contrast neighbours in a table (process | product | catalyst | conditions). Match the job in the stem, not just the topic.

Traps in Solutions

Uses the wrong arithmetic operation
Write the relationship in words before substituting (crystals = solubility at high T − solubility at low T; neutrons = A − Z; three doublings = 2³). Then check the size of the answer.
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).
Picks a related substance or process with a different role
Learn reagents and processes as one-line 'name → job' cards and contrast neighbours in a table (process | product | catalyst | conditions). Match the job in the stem, not just the topic.
Mixes up a pair of similar chemical terms
Keep a list of confusable pairs with one defining feature each and a hook. Underline the key word in the stem and check it against the definition, not the sound of the name.
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.
Uses everyday or macroscopic thinking instead of particles
Ask what the particles, ions or electrons are doing. Properties of a substance come from its particles and bonds, not from how it looks or feels.

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