Year 12 Chemistry Tutorial 9.5.E – Saponification Module 9.5 – Industrial Chemistry Topic 9.5.E – Saponification Name 1.
Date Answer true or false to the following questions. a) Glycerol is a tri-­‐ester. b) Fatty acids are long-­‐chain alkanoic acids. c) Coconut oil is a common fat used in soap making. d) Sodium stearate is a soap made from octadecanoic acid. e) Palmitic and stearic acids are unsaturated fatty acids. 2.
………………………………. ………………………………. ………………………………. ………………………………. ………………………………. Hexadecanoic acid is hydrolysed in hot sodium hydroxide solution. a)
Write a balanced chemical equation for the reaction. ………………………………………………………………………………………………………………………………………….………………………………………… b) Name the soap that forms. ………………………………………………………………………………………………………………………………………….………………………………………… c) Explain how the soap could be removed from the reaction mixture. ………………………………………………………………………………………………………………………………………….………………………………………… ………………………………………………………………………………………………………………………………………….………………………………………… ………………………………………………………………………………………………………………………………………….………………………………………… 3.
For the soap, potassium oleate (18 carbons and 1 double bond), a)
Write the molecular formula for the oleate ion. ………………………………………………………………………………………………………………………………………….………………………………………… b) Explain why this soap is classified as a surfactant. ………………………………………………………………………………………………………………………………………….………………………………………… ………………………………………………………………………………………………………………………………………….………………………………………… ………………………………………………………………………………………………………………………………………….………………………………………… c) To what class of detergents would this soap belong? ………………………………………………………………………………………………………………………………………….………………………………………… 4.
Sodium stearate does not lather in a solution of calcium chloride. a)
Classify this solution as hard or soft. ………………………………………………………………………………………………………………………………………….………………………………………… b) Use an equation to show why the soap does not lather. ………………………………………………………………………………………………………………………………………….………………………………………… ………………………………………………………………………………………………………………………………………….………………………………………… ………………………………………………………………………………………………………………………………………….………………………………………… 5.
Dodecyl alcohol ethoxylate is a synthetic detergent. Its structure is: CH3(CH2)11O(CH2CH2O)nCH2CH2OH (n=5-­‐10) a)
To what class of detergents does this substance belong? …………………………………………………………………………………………………………………………………………….……………………………………. b) Describe the properties and uses of this class. …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. c) Why is this surfactant unaffected by the presence of calcium and magnesium ions? …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. Page 2 6.
Polyphosphate compounds are added to laundry powders. They are described as ‘builders’. a)
What is the purpose of these builders? …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. b) A 1 kg pack of laundry detergent contains sodium tripolyphosphate (Na5P3O10). This sufficient for 20 washes. If the phosphorous content is 3.5% w/w, what mass of sodium tripolyphosphate is present in the washing machine in each wash? …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. c) Explain the environmental concerns of phosphate compounds in detergents. …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. …………………………………………………………………………………………………………………………………………….……………………………………. Page 3