1.9 Dicarbon monoxide, C2O, is found in dust clouds in space. The structure of this molecule is C=C=O. The molecule contains no unpaired electrons. How many lone pairs of electrons are present in a molecule of C2O? (1)  

1.25 In which reaction is the organic compound oxidised? (1)   A CH3CH2CH2CHO + Tollens’ reagent B CH3CH2CH2CHO + LiAlH4 C CH3CH2CH2OH + concentrated H3PO4 D CH3CO2C2H5 + dilute H2SO4  

1.22 Chlorofluorocarbons damage the ozone layer by undergoing reactions with a free radical mechanism. The first stage of this is initiation. Which equation is most likely to be the initiation stage when chlorofluoromethane is involved in such a reaction? (1)     Right-click on the button to open the data booklet in a new tab.     

1.11 Why is the ionic radius of a chloride ion larger than the ionic radius of a sodium ion? (1)

 1.15 A piece of rock has a mass of 2.00 g. It contains calcium carbonate, but no other basic substances. It neutralises exactly 36.0 cm3 of 0.500 mol.dm–3 hydrochloric acid. What is the percentage of calcium carbonate in the 2.00 g piece of rock?   (1)

1.19 When solid ammonium chloride dissociates at a certain temperature in a 0.500 dm3 container, ammonia and hydrogen chloride are formed.   NH4Cl (s)< == > NH3(g) + HCl (g)   The initial amount of ammonium chloride was 1.00 mol, and when the system had reached equilibrium there was 0.300 mol of ammonium chloride.   What is the numerical value of Kc for this reaction under these conditions? (1)    

1.12  Elements D and E are both in Period 3. Element D has the smallest atomic radius in Period 3. There are only two elements in Period 3 which have a lower melting point than element E. Elements D and E react together to form compound L.   (1) Which compound could be L  A  MgCl2 B MgS C Na2S D PCl 3  

1.3 The relative atomic mass of copper is 63.5. Which chart is the correct mass spectrum that would lead to this value? (1)   Right-click on the button to open the data booklet in a new tab.    

1.28 Compound X, C4H8O2, has an unbranched carbon chain. An aqueous solution of X has an approximate pH of 3.   Compound Y, C3H8O, is a secondary alcohol. X and Y are reacted together in the presence of a little concentrated sulfuric acid to form Z as the major organic product.   What is the structural formula of Z?   A (CH3)2CHCO2CH2CH2CH3 B CH3(CH2)2CO2CH(CH3)2 C CH3(CH2)2CO2(CH2)2CH3 D (CH3)2CHCO2CH(CH3)2 (1)  

 1.14 The solids sodium chloride and sodium iodide both react with concentrated sulfuric acid at room temperature.   With NaCl, the products are NaHSO4 and HCl. With NaI, the products are NaHSO4, HI, I2, SO2, H2O, S and H2S.   What is the best explanation for this difference in products?   (1)