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Chemistry Tuition Question on Organic Chemistry. (O Level / IP Chemistry)
1. Propanoic acid, C2H5CO2H, is a weak acid.
(a) Explain what is meant by the term weak acid.
(b) Propanoic acid reacts with sodium carbonate. Write the equation for this reaction.
(c) Magnesium reacts with propanoic acid to form magnesium propanoate and hydrogen.
Mg + 2C2H5CO2H  (C2H5CO2)2Mg + H2
A student added 4.80 g of magnesium to 30.0 g of propanoic acid.
(i) Which one of these reactants, magnesium or propanoic acid, is in excess? Explain your answer.
(ii) Calculate both the number of moles of hydrogen and the volume of hydrogen formed at r.t.p.
(d) Terylene has the simplified structure shown.
(i) State the functional groups on the monomers used to make Terylene.
(ii) State the type of polymerisation that occurs when Terylene is made.
State one large scale use of Terylene.
Many problems are caused by the disposal of plastics.
Describe one method of disposal of a plastic and a problem caused by this method.
Miracle Learning Centre Answer to Chemistry Tuition Question on Organic Chemistry. (O Level / IP Chemistry)
6. (a) acid which is only slightly or partly ionised/partly dissociated/not fully ionized .
(b) 2C2H5CO2H + Na2CO3 → 2C2H5CO2Na + CO2 + H2O
(c) (i) 24g of magnesium will need 2 x 74 g of propanoic acid to react so 4.8g magnesium requires 29.6g acid , so acid (30g) in excess OR
74g of propanoic acid will need ½ x 24g of Mg to react so 30g of acid requires 4.86g Mg so acid in excess (as only 4.8g Mg used) OR mol Mg = 4.8/24 = 0.2 mol acid = 30/74 = 0.405(4)/0.41 mol; 2x moles of acid required to 1 mole Mg Mg = 0.4 x 74 = 29.6g compared with 30 g acid OR 0.405/2 moles = 0.2027/0.203 moles acid compared with 0.2 moles Mg (Any two ) (ii) 0.2 mol H2 0.2 x 24 = 4.8 dm3 (d) (i) alcohols and carboxylic acids are monomers (both required) (ii) condensation (iii) clothing/named clothing/sails/conveyor or fan belts. (e) • take up landfill space because does not (bio)degrade. • incineration/burning – harmful substances/harmful fumes/harmful gases produced • recycling – difficult to sort out different polymers Learn from our Chemistry Tuition Questions and Answers. Miracle Learning Centre Call 6463 8756 or sms 8128 8342/9839 9908. (Specialist in Science and Maths) for Primary, Secondary and JC levels. Miracle Learning Centre specialises in Chemistry tuition, Physics tuition, Maths tuition and Science tuition Classes.