Coagulation

Q.

What is electrolyte concentration?

Q.

Freshly prepared precipitate sometimes gets converted to colloidal solution by?

Q.

Bleeding from a wound stops by the application of ${\mathrm{FeCl}}_3$ solution. Which of the following phenomenon takes place due to the same reason?

1. Dust particles present in the air become visible due to the passage of a narrow beam of light in a dark room.

2. Some syrupy medicines are advised to be taken after shaking the bottle.

3. A supersaturated solution slowly becomes transparent.

4. Addition of alum hastens the process of purification of water.

Q. Lyophilic colloidal sols are much more stable than lyophobic colloidal sols. This is due to the extensive solvation of lyophilic colloidal sols, which form a protective layer outside it which prevents it from forming associated colloids. Lyophilic colloidal sols also protect lyophobic colloidal sols from precipitation by the action of electrolytes. This is due to the formation of a protective layer by the lyophilic sols outside lyophobic sols. Lyophilic sols are also called protective sols.
Gelatin (lyophilic) protects gold sol (lyophobic) from coagulation on the addition of a solution of sodium chloride. The protective powers of different colloidal sols are measured in terms of gold number.
Gold number is defined as the amount of protective sol in milligrams that prevents the coagulation of 10 mL of a given gold sol on adding 1 mL of a $10\%$ solution of sodium chloride. Thus, the smaller the gold number of a lyophilic sol, the greater is the protective power.

$\left[AgI\right]I^{-}$ colloidal sol can be coagulated by the addition of a suitable cation. 1 mol $\left[AgI\right]I^{-}$ requires $AgN{O}_3,Pb(N{O}_3{)}_2$ & $Fe(N{O}_3{)}_3$ as (in moles):

1. $1,1,1$
2. $1,2,3$
3. $1,\frac{1}{2},\frac{1}{3}$
4. $6,3,2$

Q. Silver iodide is used in bringing about artificial rain because silver iodide

1. is easily decomposed in presence of sunlight
2. contains iodide ions which are large in size
3. has crystal structure similar to ice and leads to coagulation
4. being heavy, its spray brings the water droplets down

Q.

Assertion: Bleeding from a fresh cut can be stopped by applying potash alum.

Reason: Alum heals the wound created by the cut.

1. Both assertion and reason are correct and the reason is the correct explanation of the assertion.

2. Both assertion and reason are correct but the reason is not the correct explanation of the assertion.

3. Assertion is correct but the reason is incorrect.

4. Assertion is incorrect but the reason is correct.

Q. Ferric chloride is added to stop bleeding because

1. $F{e}^{3+}$ ions coagulate positively charged blood solution
2. $F{e}^{3+}$ ions coagulate negatively charged blood solution
3. $C{l}^{-}$ ions coagulate positively charged blood solution
4. $C{l}^{-}$ ions coagulate negatively charged blood solution

Q. The coagulation values in millimoles per litre of the electrolytes used for the coagulation of $A{s}_2{S}_3$ are given below:
$I.\left(NaCl\right)=52,II.\left(BaC{l}_2\right)=0.69,III.\left(MgS{O}_4\right)=0.22$
The correct order of their coagulating power is

1. I > II > III
2. II > I > III
3. III > II > I
4. III > I > II

Q. For the coagulation of 50 ml of ferric hydroxide sol, 10 ml of 0.5 M KCl is required. What is the coagulation value of $KCl$?

1. 5
2. 10
3. 100
4. None of these

Q.

The ability of an ion to bring about coagulation of a given colloid depends

upon

1. Its size

2. The magnitude of its charge only

3. The sign of its charge

4. Both the magnitude and the sign of its charge

Q.

The coagulation of 100 ml of colloidal solution of gold is completely prevented by addition of 0.25 g of a substance “X” to it before adding 1 ml of 10% NaCl solution. The gold number of “X” is

1. 0.25

2. 25

3. 250

4. 2.5

Q.

A sol has positively charged colloidal particles. Which of the following solutions is required in lowest concentration for coagulation -

1. NaCl

2. $K_4\left[Fe\right(CN{)}_6]$

3. $ZnC{l}_2$

4. $N{a}_{2}S{O}_4$

Q. Which of the following are methods to coagulate a colloidal sol?

1. Addition of Electrolytes
2. Persistent dialysis
3. Mutual coagulation
4. All of the above

Q. Molar conductivity $\left(\Lambda m\right)$ of an aqueous solution of sodium stearate, which behaves as a strong electrolyte, is
recorded at varying concentrations (c) of sodium stearate. Which one of the following plots provides the
correct representation of micelle formation in the solution?
(critical micelle concentration (CMC) is marked with an arrow in the figures)

1. 
2. 
3. 
4. 

Q. A negatively charged suspension of clay in water is needed for precipitation of minimum amount of -

1. Aluminium chloride
2. Potassium sulphate
3. Sodium hydroxide
4. Hydrochloric acid

Q. Which of the following colloids can be coagulated by $A{l}^{3+}$?

1. Haemoglobin.
2. $Ti{O}_2$
3. $A{s}_2{S}_3$
4. $CdS$

Q.

A negatively charged suspension of clay in water will need for precipitation the minimum amount of

1. Aluminium chloride

2. Potassium sulphate

3. Sodium hydroxide

4. Hydrochloric acid

Q. Ferric chloride is added to stop bleeding because

1. $F{e}^{3+}$ ions coagulate positively charged blood solution
2. $F{e}^{3+}$ ions coagulate negatively charged blood solution
3. $C{l}^{-}$ ions coagulate positively charged blood solution
4. $C{l}^{-}$ ions coagulate negatively charged blood solution

Q. Which of the following colloids can be coagulated by $A{l}^{3+}$?

1. Haemoglobin.
2. $Ti{O}_2$
3. $A{s}_2{S}_3$
4. $CdS$

Q.

Flocculation values is expressed in terms of

1. millimoles of electrolyte per litre of the sol

2. grams per litre

3. moles per litre

4. millimoles per ml

Q. The coagulating power of electrolytes having ions $N{a}^{+},A{l}^{3+}$ and $B{a}^{2+}$ for arsenic aulphide sol increase in the order

1. $A{l}^{3+}<B{a}^{2+}<N{a}^{+}$
2. $N{a}^{+}<B{a}^{2+}<A{l}^{3+}$
3. $B{a}^{2+}<N{a}^{2+}<A{l}^{3+}$
4. $A{l}^{3+}<N{a}^{+}<B{a}^{2+}$