Preparing a Standard Solution for H2 Chemistry Paper 4

Q: What is the correct way to prepare a standard solution in H2 Chemistry Paper 4?
A: Calculate the required mass, weigh by difference, dissolve the solid fully, transfer all solution and washings into a volumetric flask, make up to the calibration mark, stopper, invert repeatedly, and label the final solution clearly.

Fast answer for Paper 4
The most important scoring phrase is quantitative transfer. Rinse the beaker, stirring rod, and funnel with deionised water, and add every washing to the volumetric flask before making up to the mark. Otherwise some solute is left behind and the prepared concentration is too low.

Quick standard-solution map

• The concentration depends on mass and final volume: Calculate $m = cVM_r$.
• Quantitative transfer prevents solute loss: Rinse every container and add washings to the flask.
• The meniscus and mixing decide final accuracy: Make to the mark carefully, stopper, and invert repeatedly.

Concrete example: If crystals remain in the beaker after transfer, the solution in the flask contains less solute than calculated. The prepared concentration is too low even if the final meniscus is correct.

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