Lakshya Education MCQs

Question: 104 g of gelatin is required to be added to 100 cm3 of a stanadard gold solution to just prevent its precipitation by addition of 1 cm3 of 10% NaCl solution to it. Hence, gold number of gelatin is?
Options:
A.10
B.1
C.0.1
D.0.01
Answer: Option D
: D

104g=0.1mg
100cm3 of gold sol require 0.1 mg
10cm3 of gold sol will required 0.01 mg
Hence, gold number = 0.01.

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Question 1. Glutamic acid H2NCH(CH2CH2COOH)COOHN has pKa1(αCOOH)=2.2,pKa2(R group COOH)=4.3. The isoelectric point of glutamic acid is
  1.    5.9
  2.    7.0
  3.    10.2
  4.    3.2
Answer: Option D
: D

H3+NCH|CH2CH2COOHCationicformCOOHOnneutralisation1stionizationH3+NCH|CH2CH2COOHCOO2ndionizationH3+NCH|CH2CH2COOCOO

Isoelectricpoin(pI)=pKa1+pKa32
2.2+4.32=3.25
Question 2. The volume of colloidal particle Vc as comapred to the volume of solute particle in a true solution Vs could be
  1.    VcVs=1
  2.    VcVs=1023
  3.    VcVs=10−3
  4.    VcVs=103
Answer: Option D
: D

Diameter of colloidal particle is about 10 times larger than solute particles in a true solution. Hence, volume is about 1000 times greater i.e. VcVs=103
Question 3. Which of the following is an example of oil dispersed in water emulsion:
  1.    Butter
  2.    Milk
  3.    Cream
  4.    None of the above
Answer: Option B
: B

In milk, liquid fat is dispersed in water.
Question 4. Which of the following factors are responsible for the stability of lyophilic sols?
  1.    Charge on the colloidal particles
  2.    Solvation of colloidal particles
  3.    Both a and b
  4.    None of the above
Answer: Option C
: C

The two factors responsible for the stability of the lyophilic sols are the charge and solvation of the colloidal particles.
Question 5. Milk can be preserved by adding a few drops of
  1.    Formic acid solution 
  2.    Formaldehyde solution
  3.    Acetic acid solution
  4.    Acetaldehyde solution
Answer: Option B
: B

Formaldehyde is an emulsifier
Question 6. 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
Answer: Option C
: C

Ag+I ions brings about coagulation of water droplets easily.

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