Rate equation and rate constant
rate = k[A]m[B]n
Orders come from rate data, not balancing coefficients, and k units follow from the final rate equation.
Work it, then mark it
Do each calculation on paper first, then reveal the mark scheme and tick the marks you actually earned — the same way you should mark past papers.
Doubling [A] while [B] is constant makes rate four times larger. Doubling [B] while [A] is constant has no effect. When [A] = 0.200 mol/dm3, rate = 0.0360 mol/dm3/s. Deduce the rate equation and calculate k with units.
Do the calculation on paper first — then mark it.
Where the marks get lost
- Reading reaction orders from the balanced equation.
- Quoting k without deriving its units from rate divided by concentration powers.
Exam tip: Compare pairs where only one concentration changes, then substitute into the completed rate equation.
Calculations are the most trainable marks in chemistry
They come up every paper and reward a clean method. Send me one you keep dropping marks on — your first lesson is free.