The label from a bottle of pine fresh bleach cleaner is shown - Scottish Highers Chemistry - Question 12 - 2019
Question 12
The label from a bottle of pine fresh bleach cleaner is shown.
PINE FRESH BLEACH CLEANER
WARNING! Do not use together with other products.
May release dangerous ga... show full transcript
Worked Solution & Example Answer:The label from a bottle of pine fresh bleach cleaner is shown - Scottish Highers Chemistry - Question 12 - 2019
Step 1
Complete the table for compound B.
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Answer
The answer should identify compound B as an ionic surfactant with a positively charged head group, thus filling in the table as follows:
| Compound B | ionic | positively charged |
Step 2
Soaps can be made from fats and oils.
Name the reaction used to make soaps from fats and oils.
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The reaction used to make soaps from fats and oils is called saponification, which is an alkaline hydrolysis reaction.
Step 3
Explain fully the cleaning action of compound C.
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Soap molecules, such as compound C, have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts. The hydrophilic head attaches to water while the hydrophobic tail attaches to grease or oil. This allows the soap to encapsulate dirt and grease in micelles, which can then be rinsed away with water. Additionally, soap reduces the surface tension of water, improving its ability to spread and penetrate into dirty surfaces.
Step 4
State how emulsifiers are made from edible oils.
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Emulsifiers are produced by reacting edible oils with glycerol and specific triols, which leads to the formation of structures that can stabilize emulsions by having both hydrophilic and hydrophobic regions.
Step 5
Explain what is meant by a pure covalent bond.
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A pure covalent bond occurs when two atoms share electrons equally, resulting in no charge separation. This typically occurs between identical non-metal atoms where the electronegativity is the same.
Step 6
Suggest why this occurs.
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The reaction occurs because the formation of NaOCl is energetically favorable, allowing the chlorine gas to react with sodium hydroxide to produce the hypochlorite ion instead of remaining unreacted.
Step 7
Explain clearly why mixing the bleach with an acid would shift the equilibrium to the right, increasing the release of chlorine gas from the bleach cleaner.
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Adding an acid increases the concentration of H+ ions in the solution. According to Le Chatelier's principle, this shift will counteract the change by favoring the formation of chlorine gas (Cl2), thus driving the reaction to the right and increasing the release of Cl2 from the bleach.
Step 8
Write the ion-electron equation for the reduction reaction taking place in Step 1.
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The ion-electron equation is:
OCl−+2H++2e−→Cl2+H2O
Step 9
Calculate the concentration, in mol l-1, of sodium hypochlorite in the bleach.
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To find the concentration of sodium hypochlorite, first calculate the moles of thiosulfate using its concentration and the volume used in the titration:
From the stoichiometric relationship of the reactions:
1 mole of OCl- reacts with 2 moles of Na2S2O3, thus moles of OCl- = 0.000882 ext{ mol} / 2 = 0.000441 ext{ mol}.
Given that the volume of bleach sample is 25 cm³ or 0.025 dm³:
