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AQA A-Level Chemistry Paper 3 Exam 2025 Questions and Answers Key apparatus for preparation of a standard solution? - --CORRECT ANSWER-Volumetric flask, pipette and filler, burette, conical flask, white tile. How do you ensure an accurate standard solution? - --CORRECT ANSWER--Use a mass balance to weigh solute accurately, dissolve fully in deionised water, and rinse all equipment into the volumetric flask before making up to the line. Why is a white tile used in titrations? - --CORRECT ANSWER--To help detect the colour change more clearly at the end point. What indicators are used in acid-base titrations and why? - --CORRECT ANSWER--Phenolphthalein (pink in alkali, colourless in acid) or methyl orange (yellow in alkali, red in acid) - depending on strong/weak acid or base used. How do you ensure accurate titration results? - --CORRECT ANSWER--Repeat until concordant titres (within 0.1 cm³), swirl the flask, add dropwise near end point, rinse burette tip. How is heat energy calculated? - --CORRECT ANSWER--∆Q = mc∆T ....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 1