SURFACE CHEMISTRY Quiz-8

SURFACE CHEMISTRY QUIZ-8

Dear Readers,

IIT JEE exam which consists of JEE Main and JEE Advanced is one of the most important entrance exams for engineering aspirants. The exam is held for candidates who are aspiring to pursue a career in the field of engineering and technical studies. Chemistry is important because everything you do is chemistry! Even your body is made of chemicals. Chemical reactions occur when you breathe, eat, or just sit there reading. All matter is made of chemicals, so the importance of chemistry is that it's the study of everything..

Q1. Statement 1: A colloidal state, a dispersion of a dispersed phase in a dispersion medium is a heterogeneous state. Statement 2: The particle size of dispersed phase ranges between true solution and suspension state.

•  Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•  Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•  Statement 1 is True, Statement 2 is False
•  Statement 1 is False, Statement 2 is True

Solution
(c). Explanation is correct reason for statement.

Q2.  Statement 1: A catalyst increases the rate of a reaction.
Statement 2: In presence of a catalyst, the activation energy of the reaction increases.

•  Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•  Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•  Statement 1 is True, Statement 2 is False
•  Statement 1 is False, Statement 2 is True

Solution
(c). A catalyst increases the rate of reaction because in the presence of catalyst the activation energy of the reaction and decreases.

Q3.Statement 1: Sol particles show Tyndall effect. Statement 2: The scattering is directly proportional to size of sol particle.

•   Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•  Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•  Statement 1 is True, Statement 2 is False
•  Statement 1 is False, Statement 2 is True

Solution
(c). Sol particles show Tyndall effect due to scattering of light. Also the scattering is directly proportional to size of sol particles.

Q4. Statement 1: A reaction cannot become fast by itself unless a catalyst is added
Statement 2: A catalyst always increases the speed of a reaction.

•  Statement 1 is True, Statement 2 is True; Statement 2 is correct explanation for Statement 1
•  Statement 1 is True, Statement 2 is True; Statement 2 is not correct explanation for Statement 1
•  Statement 1 is True, Statement 2 is False
•  Statement 1 is False, Statement 2 is True

Solution
(d). There are reactions in which one of the products acts as catalyst (autocatalysis) and no catalyst is added.

Q5.Freundlich adsorption isotherm is obeyed by the adsorptions where the adsorbate forms a multimolecular layer on the surface of adsorbent. In such case, the degree of adsorption varies linearly with pressure but at high pressure, it becomes independent of pressure. It is given as x/m=kp^(1/n) Where, k and n constants Langmuir adsorption isotherm is obeyed by the adsorption where the adsorbate forms only a unimolecular adsorbed layer. The mathematical relation of Langmuir adsorption isotherm is x/m=ap/(1+bp). Q. When log⁡(x/m) is plotted against log⁡p, we get a straight line with slope

•  1/n
•  n
•  x
•  m

Solution
 option-(a).

Q6. Emulsions are also the colloidal solutions in which disperse phase as well as dispersions medium are liquids. It may be oil in water or water in oil type. Bancroft proposed that the phase in which the emulsifier is more soluble becomes the outer phase of the emulsion. Emulsifiers can be used to stabilize the emulsion. Soaps, detergents, proteins and gum etc, are used as emulsifiers. Q. Addition of lyophilic solution to the emulsion forms

•  A protective film around the dispersed phase
•  A protective film around the dispersion medium
• An aerosol
•  True Solution

Solution
(a). Addition of lyophilic solution to the emulsion forms a protective film around the dispersed phase.

Q7.A chemist studied the phenomenon of adsorption by putting blood charcoal in KCl solution. He observed difference in the behaviour with dilute KCl solution and with concentrated KCl solution. He also studied the adsorption of different gases on solid adsorbent and the effect of temperature on adsorption. He put forward a mathematical relationship relating x/m with equilibrium pressure. Q. Which of the following is correct?

•  Adsorption is always exothermic?
•  Adsorption is always endothermic
•  Physical adsorption is endothermic whereas chemisorptions is exothermic.
•  Chemical adsorption is endothermic whereas physical adsorption is exothermic

Solution
(a). Adsorption is always exothermic

Q8.Colloidal dispersion have been classified into different types depending upon the physical state of the dispersed phase and the dispersion medium. They are prepared in the industry or in the laboratory by a number of methods and then purified. The protective action of lyophilic colloids was studied by zsigmondy and he introduced a term called gold number. Q. Which of the following does not form a lyophilic colloid?

•  Rubber dissolved in benzene 1
•  White of the egg dissolved into water
•  Common salt added into benzene
•  Stannous chloride solution added to gold chloride solution

Solution
(d). SnCl2+AuCl3 react to form gold sol which is a lyophobic sol.

Q9.The gold number of gelatin is 0.01. Calculate the amount of gelatin to be added to 1000 mL of a colloidal sol of gold to prevent its coagulation, before adding 1 mL of 10% NaCl solution

•  2
•  1
•  4
•  5

Solution
(b). Gold number of gelatin = 0.01 or 0.01 mg gelatin required to be added to 10 mL of gold sol to completely prevent coagulation of 1 mL of 10% NaCl solution Therefore gelatin added to 1000 mL of gold sol to prevent coagulation =(0.01×1000)/10=1 mg

Q10. From the given following sol how many can coagulate silica acid sol? Fe(OH)3,Ca(OH)2,Al(OH)3, Starch, Clay, As2S3,CdS, Basic dye

•  4
•  3
•  2
• 8

Solution
(a). Silicic acid is negatively charged sol. Hence the sol with positive charge can coagulate silicic acid, i.e., Fe(OH)3,Ca(OH)2,Al(OH)3, basic dye

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