IGCSE Chemistry Written Exam 2024.

IGCSE Chemistry Written Exam 2024. State the method used to obtain sand from a mixture of sand and water - CORRECT ANSWER filtration State the method used to obtain solid copper sulfate from aqueous copper sulfate - CORRECT ANSWER crystallisation State the method used to obtain red food dye from a mixture of food dyes - CORRECT ANSWER paper chromatography State the method used to obtain water from salt water - CORRECT ANSWER simple distillation Draw a diagram to show equipment used in simple distillation - CORRECT ANSWER For what process is this equipment used? State the method used to obtain kerosene from a crude oil. - CORRECT ANSWER fractional distillation Draw the equipment used in fractional distillation in the lab - CORRECT ANSWER For what process is this equipment used? Explain how fractional distillation is used to separate a mixture of different liquids - CORRECT ANSWER The different liquids have different boiling points State the method used to extract the red dye from a sample of rose petals - CORRECT ANSWER dissolving Describe how pure salt can be obtained from rock salt - CORRECT ANSWER 1) Grind rock salt into a fine powder. 2) Add powder to hot water and stir to dissolve salt. 3) Filter mixture. Salt solution passes through the filter paper leaving behind the sand. 4) Boil filtrate to evaporate some of the water. 5) Leave saturated solution to cool so that crystals of salt form. 6) Filter cold mixture to separate the crystals from the remaining solution. Ethanol is a flammable liquid. Suggest how it could be heated safely - CORRECT ANSWER Use a water bath Explain how a chromatogram shows that different dyes are different from each other - CORRECT ANSWER Each dyes has a different mixture State the expression for calculating molar concentration - CORRECT ANSWER Molar concentration = Amount (in moles)/volume (in dm^³) Which cation gives a crimson red flame colour? - CORRECT ANSWER Li⁺ Which cation gives a orange flame colour? - CORRECT ANSWER Na⁺ Which cation gives a lilac flame colour? - CORRECT ANSWER K⁺ Which cation gives a brick red flame colour? - CORRECT ANSWER Ca²⁺ Describe how you would carry out a flame test - CORRECT ANSWER Put solid onto a wire. Put into a blue flame How would you test for the ammonium ion? - CORRECT ANSWER Add sodium hydroxide. If ammonium ions were present, ammonia gas will form which will turn damp red litmus paper blue