Question detail

Case 75 formula-choice. A student starts a worked solution. Which first step is most appropriate? Focus on concentration mol/dm3 mass solute and volume in Concentrations in mol/dm3 and titration calculations, not on a neighbouring Unit 4.3 idea.

Try the question, check the answer, then read the explanation to understand the curriculum point.

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At a glance

MCQ

Type

practice

Style

Topic

Using concentrations of solutions in mol/dm3 (chemistry only) (HT only)

Question

A. Case 75 formula-choice: Use the named relationship before substituting numbers for concentration mol/dm3 mass solute and volume
B. Case 75 formula-choice: Start with a memorised answer and add a unit later (Concentrations in mol/dm3 and titration calculations)
C. Case 75 formula-choice: Change every number into a percentage before choosing a formula (concentration mol/dm3 mass solute and volume)
D. Case 75 formula-choice: Use a nearby formula from a different quantitative chemistry subtopic (Using concentrations of solutions in mol/dm3 (chemistry only) (HT only))

Answer

The correct option is Case 75 formula-choice: Use the named relationship before substituting numbers for concentration mol/dm3 mass solute and volume.

Explanation

The correct option is Case 75 formula-choice: Use the named relationship before substituting numbers for concentration mol/dm3 mass solute and volume. It supports the approved learning objective by keeping the method tied to concentration mol/dm3 mass solute and volume in Concentrations in mol/dm3 and titration calculations. The other options are incorrect because they either use the wrong quantitative relationship, lose the required unit, confuse coefficients with subscripts, or report an answer without a complete worked method.

Common mistake

Incorrect Unit Conversion

Students often forget to convert volumes from cm3 to dm3 when calculating concentration in mol/dm3.

Always convert cm3 to dm3 by dividing the volume in cm3 by 1000 before using it in concentration calculations.

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For Concentrations in mol/dm3 and titration calculations, which exam wording answer best supports this Unit 4.3 objective: (chemistry only) (HT only) Calculate concentration in mol/dm3 from mass of solute and volume?