2.The relative molecular mass of an element X is 124. What is its molecular formula?(Ar(X)=31)
3. 5.42g of a chloride of mercury gives on decomposition 1.42g of chlorine. If the chloride has a formula mass of 272, what is its chemical formula?
4. A metal M forms ions of charge 3+. 6.21g of M comvines with 11.04g of sulphur to form an ionic sulphide. Find the atomic mass of M.
1. calculate the mass of hydrogen gas that can be obrained by adding 15g calucium into 12g water. Give a balanced equation. (one of them is in excess)
2.Chlorine reacts with sulphur to form a compound with relative molecular mass of 135.2 The compound contains 52.5% of chlorine by mass. (i) Deduce the molecular formula of compound (ii) draw the electronic diagram of the compound.
3. Nitrogen gas can be produced by passing dry ammonia gas over an excess of hot copper(II)oxide. (a) At the end of the experiment, some reddish brown powder was formed on the copper(ii) . Name this poweder.
(continue)3(b)Write an equation for the reaction involved. (C)Calculate the mass of nitrogen gas that can be obtained from 20g of copper(II) oxide. (d) Describe breifly how you would obtain the reddish brown powder mentioned in (a) from its mixture with the copper(II)oxide.
4. Lead can be obtained by heating lead(II)sulphide with oxygen in stage1 and then heat in a blast furnace with coke(carbon) in stage2. Assuming that coke contains 90% of usable carbon, calculate the mass of coke needed to extract lead from 5000kg of lead(II) oxide.
