2.3. Formulas
A subsection of Chemistry, 9701, through 2. Atoms, molecules and stoichiometry
Listing 10 of 88 questions
Ethanedioicacid, HO2CCO2H, has a relative molecular mass of 90.0. Explain what is meant by the term relative molecular mass. State the empirical formula of ethanedioicacid. Calculate how many atoms of carbon are present in 0.18 g of ethanedioicacid, HO2CCO2H. Show your working.  atoms of carbon present = Solid ethanedioic acid reacts with aqueous calcium ions to make a precipitate of calciumethanedioate, CaC2O4. CaC2O4 breaks down when heated to form calciumoxide, carbondioxide and carbonmonoxide. Construct an equation to represent the reaction of CaC2O4 when heated. Include state symbols. Identify the type of reaction which occurs when CaC2O4 is heated. Identify another compound containing calcium ions which will also produce carbondioxide and calciumoxide when it is heated. 
9701_s21_qp_21
THEORY
2021
Paper 2, Variant 1
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Compound A is an organic compound which contains carbon, hydrogen and oxygen. When 0.240 g of the vapour of A is slowly passed over a large quantity of heated copper(oxide, CuO, the organic compound A is completely oxidised to carbon dioxide and water. Copper is the only other product of the reaction. The products are collected and it is found that 0.352 g of CO2 and 0.144 g of H2O are formed. In this section, give your answers to three decimal places. Calculate the mass of carbon present in 0.352 g of CO2. Use this value to calculate the amount, in moles, of carbon atoms present in 0.240 g of A. Calculate the mass of hydrogen present in 0.144 g of H2O. Use this value to calculate the amount, in moles, of hydrogen atoms present in 0.240 g of A. Use your answers to calculate the mass of oxygen present in 0.240 g of A. Use this value to calculate the amount, in moles, of oxygen atoms present in 0.240 g of A. Use your answers to to calculate the empirical formula of A. When a 0.148 g sample of A was vapourised at 60oC, the vapour occupied a volume of 67.7 cm3 at a pressure of 101 kPa. Use the general gas equation pV = nRT to calculate Mr of A. Mr = Hence calculate the molecular formula of A. Compound A is a liquid which does not react with 2,4-dinitrophenylhydrazine reagent or with aqueous bromine. Suggest two structural formulae for A. Compound A contains only carbon, hydrogen and oxygen. Explain how the information on the opposite page about the reaction of A with CuO confirms this statement.
9701_w11_qp_21
THEORY
2011
Paper 2, Variant 1
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Questions Discovered
88