Tag: soap

Questions Related to soap

Statement: Detergents give scum with hard water.


State whether the given statement is true or false.

  1. True

  2. False


Correct Option: B
Explanation:

Detergents are not soaps. Detergents work by coming in contact with a surface and reducing surface tension, with something known as a surfactant. Basically allowing the dirt to slide away. Detergents are synthetics. Soap is natural, like glycerine or tallow.But they are very active in hard water.
One reason why laundry detergents work better than soap is that they contain substances that soften the water. Hard water contains dissolved calcium $Ca^{+2}$ and magnesium $Mg^{+2}$ ions. These ions interfere with the action of soap by reacting with it to form a gray, slimy substance called curd or soap scum. Laundry detergents inhibit curd formation because they contain substances such as sodium carbonate $(NaCO _{3})$ that removes the Ca and Mg ions from the water. When sodium carbonate dissolves in water it separates to form Na ions and $CO _{3}$ ions. The dissolved $CO _{3}$ ions react with the Ca and Mg to form $CaCO _{3}$ and $MgCO _{3}$ which are solids and settle to the bottom of the washer. Hence given statement is false because it given scum even in soft water but not that much.

Soaps are water soluble while detergents are water insoluble.

  1. True

  2. False


Correct Option: B
Explanation:

Soaps are water-soluble sodium or potassium salts of fatty acids. Soaps are made from fats and oils, or their fatty acids, by treating them chemically with a strong alkali.
detergent is a surfactant, usually alkylbenzenesulfonates , a family of compounds that are similar to soap but are more soluble in hard water, because the polar sulfonate (of detergents) is less likely than the polar carboxyl (of soap) to bind to calcium and other ions found in hard water.Option B is correct.

What change will you observe if you test soap with litmus paper (red and blue)?

  1. It will turn red litmus blue

  2. It will turn blue to red

  3. Red litmus paper won't change colour

  4. None of these


Correct Option: A
Explanation:

Since, soaps are basic in nature, thus, it turns red litmus paper to blue. When blue litmus paper is dipped in soap solution, it remains blue.


Option A is correct.

Micelle formation take place when soap is added to water? Will a micelle be formed in other solvents like ethanol also?

  1. True

  2. False


Correct Option: B
Explanation:

A molecule of soap has two dissimilar ends. At one end is the hydrocarbon chain which is water repellent. At the other end carboxylate anion is present which is water soluble end. When soap is dissolved in water, many molecules come together and form a group called micelle, these micelles are formed because their hydrocarbon chains come together and the polar ends are projected outward. Micelle formation in ethanol will not occur because the hydrocarbon chain end of the soap will also dissolve in water.

State True or False:
Statement : The polar end in soap is called hydrophilic end.

  1. True

  2. False


Correct Option: A
Explanation:

The soap molecule is very long. One end is polar (unequal sharing of electrons) and the other end is not (equal sharing of electrons). The polar end grabs onto a water molecule hence called hydrophilic. Hence the given statement is true.

Washing powders contain detergents in the range of (by mass):

  1. $10-15\%$

  2. $15-30\%$

  3. $50-60\%$

  4. $40-50\%$


Correct Option: B
Explanation:

Modern synthetic detergents are alkyl or aryl sulphonates produced from petroleum (or coal) and sulphuric acid. They can be defined as the sodium or potassium salt of a long chain alkyl benzene sulphonic acid or the sodium or potassium salt of a long chain alkyl hydrogen sulphate, that has cleansing properties in water.
They are used in washing powders in a proportion of about $15-30\%$.

Which of the following substance has bitter taste?

  1. Milk

  2. Amla

  3. Soap solution

  4. Salt solution


Correct Option: C
Explanation:

Soaps are obtained by treating vegetable or animal oils and fats with a strong alkaline solution. Basic solutions are bitter in taste.

Soaps are sodium salts of :

  1. mineral acids

  2. fatty acids

  3. bases

  4. carbonic acid


Correct Option: B
Explanation:

Soap is a salt of fatty acid. These are obtained by treating vegetable or animal oils and fats with strong alkaline solution. Fats and oils are composed of triglycerides,three molecules of fatty acids are attached to a single molecule of glycerol. This alkaline solution often called as lye brings about a chemical reaction known as saponification.

A detergent is :

  1. cleaning agent

  2. drugs

  3. soap

  4. catalyst


Correct Option: A
Explanation:

A detergent is a cleaning agent.

Soaps are:

  1. sodium or potassium salts of higher fatty acid

  2. esters of higher fatty acids

  3. glycerides of fatty acids

  4. hydrides of fatty acids


Correct Option: A
Explanation:
Soaps are water-soluble sodium or potassium salts of fatty acids. Soaps are made from fats and oils, or their fatty acids, by treating them chemically with a strong alkali. 
$C _{12}H _{35}COONa$ is a good example of soap. 

Hence, option $A$ is correct.