OCR ANSWER AND SOLUTIONS

1 How many electrons are in a 12Mg 24 2+ ion? A 10 B 12 C 14 D 22 Your answer - ANSWER A 2 What is the formula of chromium(III) sulfate? A Cr3SO4 B Cr(SO4)3 C Cr2(SO4)3 D Cr3SO3 Your answer - ANSWER C 3 Which molecule is non-polar? A SF6 B H2S C PF3 D NH3 Your answer - ANSWER A 4 Which row is correct? Highest pH when added to water Most reactive halogen A MgO F2 B MgO I2 C BaO F2 D BaO I2 - ANSWER C 5 Which equation represents a redox reaction? A Mg + 2HCl → MgCl2 + H2 B MgO + 2HCl → H2O + MgCl2 C MgCO3+ 2HCl → CO2 + H2O + MgCl2 D Mg(OH)2 + 2HCl → MgCl2 + 2H2O - ANSWER A 6 This question is about trends in the periodic table. Which trend is correct? A melting point decreases from lithium to carbon B boiling point decreases from fluorine to iodine C first ionisation energy decreases from lithium to caesium D first ionisation energy increases from nitrogen to oxygen - ANSWER C 7 A sample of a compound M contains 1.46 g of carbon, 0.482 g of hydrogen and 1.69 g of nitrogen. What is the empirical formula of M? A CH2N B C4HN4 C CH4N D C2H4N - ANSWER C 8 A student mixes 100 cm3 of 0.200 mol dm-3 NaCl(aq) with 100 cm3 of 0.200 mol dm-3 Na2CO3(aq). What is the total concentration of Na+ ions in the mixture formed? A 0.100 mol dm-3 B 0.200 mol dm-3 C 0.300 mol dm-3 D 0.400 mol dm-3 - ANSWER C 9 Which mass of substance contains the greatest number of atoms? A 3.00 g of ammonia, NH3 B 3.00 g of chloromethane, CHCl3 C 4.00 g of hydrogen sulfide, H2S D 4.00 g of hydrogen chloride, HCl - ANSWER A