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chem 05 LQ q10 and 06 LQ q9 急
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chem 05 LQ q10 and 06 LQ q9 急 請附解譯 唔明06 9b(ii)同05 10b~ 更新: ce
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for 05 10b (i) the mass of gas liberated from the reaction: according to the lose of mass in conical flask When gas is evolved, it will flow out from the conical flask because there are spaces in the cotton wool for the gas to escape. The question says you may assume the gas is NOT soluble in water that means the all the gas is escaped So take the difference of the initial reading and the final reading of the flask (ii)no of moles of gas evolved=no of moles of sodium hydrogencarbonate reacted (iii) (iv)The main factors of the rate of reaction 1. concentration 2. surface area 3. temperature in this question, higher temperature water is used because higher temperature means particles of reactants move faster so reaction rate increases 06 9b(ii) The assumption says there are no substances in the 'Soda ash' that can react with hydrochloric acid but it did not say that the 'Soda ash' contains pure sodium carbonate There are impurities in 'soda ash' but do not react with hydrochloric acid Step for the question 1.write down the formula 2.calculate the no of moles of the known one (Hydrochloric acid) 3.use ratio to calculate the substance which the question ask (sodium hydroxide) 4.calculate what the substance the question want (i.e. % of mass of sodium carbonate)
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