IB Chemistry SL Reactivity 3: What are the mechanisms of chemical change? questions

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Question 1

Multiple choiceEasy1 mark

Four monoprotic acids are prepared as aqueous solutions at the same temperature and with the same initial concentration. Which sample contains the weakest acid?

PQRS020406080100Acid sampleAcid particles ionized / %
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Answer: B. At equal initial concentration and temperature, the weakest acid ionizes to the smallest extent. Sample S has the smallest ionized fraction, 5%, so it is the weakest.

A: Q is partially ionized, but choosing it ignores the still smaller ionized fraction for S.
C: P has the greatest ionization, 100%; this reverses the relationship and identifies the strongest acid.
D: R has a smaller ionized fraction than Q, but its 20% exceeds S’s 5%.

Remember: compare the extent of ionization, not the initial concentration.

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