I am doing an experiment on saponification. we conducted a hard water test at th
ID: 992570 • Letter: I
Question
I am doing an experiment on saponification. we conducted a hard water test at the end with 4 different test tubes. this experiment went as follows
"Hard Water Reactions.
Place about one-third spatula full of the soap you have prepared in a 50-mL beaker containing 25 mL of water.
Warm the beaker with its contents to dissolve the soap.
Pour 5 mL of the soap solution into each of 5 test tubes (nos. 1, 2, 3, 4, and 5).
Test no. 1 with 2 drops of a 5% solution of calcium chloride (5% CaCl2), no. 2
with 2 drops of a 5% solution of magnesium chloride (5% MgCl2), no. 3 with 2 drops of a 5% solution of iron(III) chloride (5% FeCl3), and no. 4 with tap water. The no. 5 tube will be used for a basicity test, which will be performed later.
Record your observations on the Report Sheet. "
OUR RESULTS ARE AS FOLLOWS
test tube #4 (water) : Solution turned an thick orange color, no transparency
Test tube #3 (iron III chloride): Solution turned an thick orange color, no transparency
test tube #2 (magnesium chloride): Solution turned an extremely cloudy color, no transparency
test tube #1 (calcium chloride): Solution turned a cloudy white color, solid particle was formed in the middle along with a few bubbles on the top
my question is, what do the results for each test tube mean? i am having trouble writing up my discussion. the full lab link is as follows: http://www.seattlecentral.edu/faculty/ptran/bastyr/Summer%2006/organic/Organic%20Exp/Experiment4Preparation%20and%20properties%20of%20a%20soap1.pdf
Explanation / Answer
Soaps are produced during the chemical reaction known as saponification.
Saponification is the reaction between a fat or oil and a base, producing glycerol and a salt (soap)
fat or oil + base -----> glycerol + salt (soap)
Soaps are usually sodium or potassium salts of long-chain fatty acids
Example
This is the general formula of soap CH3(CH2)16COO-Na+
Most soaps are made from vegetable oils such as olive oil, palm oil and coconut oil.
it does not function well in acidic solutions because of the formation of insoluble fatty acid
eg, CH3(CH2)16COO-Na+(aq) + HCl(aq) -----> CH3(CH2)16COOH(s) + Na+(aq) + Cl-(aq)
it forms insoluble precipitates with Ca2+ and Mg2+ ions present in hard water, forming a scum
eg, 2CH3(CH2)16COO-Na+(aq) + Ca2+(aq) -----> [CH3(CH2)16COO-]2Ca2+(s) + 2Na+(aq)
So what you are seeing in thise reactions are the salts of the respective fatty acids, which are now insoluble in water, like fatty acid salt of iron in test tube 3 which is coloured due to the colour of iron.
The fatty acid salts of Ca2+ and Mg2+ in test tube 1 and 2
The fatty acid salt of all salts present in hard tap water in test tube 4.
glyceryl tristearate(ester) + NaOH
(base) ---> glycerol
(alkanol) + sodium stearate
(salt, soap)
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