Tag: chemistry

Questions Related to chemistry

 $SO _2(g) + 1/2O _2 (g)\rightleftharpoons SO _3(g) \Delta H^o _{298} = 98.32 kJ/mole, \Delta S^o _{298} = 95.0 J/K/mole$.


 Find the $K _p$ for this above reaction at 298K:

chemistry chemical equilibrium relationship between equilibrium constant, reaction quotient and gibbs energy law of mass action chemical equilibrium and acids-bases

  1. $K _P = 9.31 \times 10^{-12} atm^{1/2}$

  2. $K _P = 5.34 \times 10^{-13} atm^{1/2}$

  3. $K _P = 3.7 \times 10^{-13} atm^{1/2}$

  4. $K _P = 3.7 \times 10^{-14} atm^{1/2}$

Show answer
Correct Option: B
Explanation:
$\displaystyle \Delta G^0 = \Delta H^0 - T\Delta S^0  $
$\displaystyle  \Delta G^0 =  98.32 \times 1000 - 298 \times 95.0 = 70010 J/mol$
$\displaystyle  \Delta G^0 = -RTlnK _P$
$\displaystyle 70010 = - 8.314 \times 298 \times ln K $
$\displaystyle  ln K = -28.26$
$\displaystyle  K = 5.34 \times 10^{-13}$

Which of the following statements are correct?
(i)   When an animal hide, which has negatively charged particles, is soaked in tannin, which contains positively charged colloidal particles, mutual coagulation does not take place.
(ii) Photographic films are prepared by coating an emulsion of the light sensitive silver bromide in gelatin over glass plates or celluloid films.
(iii) Latex is a colloidal solution of rubber particles which are negatively charged.
(iv) In Cottrell precipitator, the smoke, before it comes out from the chimney, is led through a chamber containing plates having a charge opposite to that carried by smoke particles. The particles on coming in contact with these plates acquire some charge and do not get precipitated.

chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

  1. (i) and (iv) only

  2. (ii) and (iii) only

  3. (ii), (iii) and (iv) only

  4. All of these.

Show answer
Correct Option: B
Explanation:

There are various applications of colloids-

    • Tanning: Animal hides are colloidal in nature. When a hide, which has positively charged particles, is soaked in tannin, which contains negatively charged colloidal particles, mutual coagulation takes place. This results in the hardening of leather. This process is termed as tanning. Chromium salts are also used in place of tannin.
    • Photographic plates and films: Photographic plates or films are prepared by coating an emulsion of the light-sensitive silver bromide in gelatin over glass plates or celluloid films.
    • Rubber industry: Latex is a colloidal solution of rubber particles which are negatively charged. Rubber is obtained by coagulation of latex.
    • Electrical precipitation of smoke: Smoke is a colloidal solution of solid particles such as carbon, arsenic compounds, dust, etc., in air. The smoke, before it comes out from the chimney, is led through a chamber containing plates having a charge opposite to that carried by smoke particles. The particles on coming in contact with these plates lose their charge and get precipitated. The particles thus settle down on the floor of the chamber. The precipitator is called Cottrell precipitator.
    Hence, option B shows the correct statements.

        Some medicines are more effective in the colloidal form because of:

        chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

        1. the charged colloidal particles present in it

        2. the large surface area and easy assimilation

        3. precipitation of medicine in the blood

        4. the stabilisation of medicine in colloidal form

        Show answer
        Correct Option: B
        Explanation:
        • A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium.
        • Colloidal medicines are more effective because they have large surface area and are therefore easily assimilated.

        Various applications of collids are-
        • Purification of drinking water
        • Cleansing action of soaps and detergents as Medicines
        • Photographic plates and films

        Which reagent, when mixed with ammonium sulfate and then heated, liberates ammonia?

        chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

        1. aqueous bromine

        2. dilute hydrochloric acid

        3. limewater

        4. potassium dichormate (VI) in acidic solution

        Show answer
        Correct Option: C
        Explanation:
        Test for the ammonium ion is adding a base then warming and then ammonia gas is produced therefore answer is C because limewater is $Ca(OH) _2$ which is a base and when it reacts with an ammonium ion which ammonium sulphate it produces ammonia gas overall reaction is:
        $Ca(OH) _2 + (NH _4) _2SO _4 \rightarrow CaSO _4 + 2NH _3 + 2H _2O$

        Tanning of leather is the :

        chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

        1. colouring of leather by chemicals

        2. drying process to make the leather hard

        3. polishing of leather to make it look attractive

        4. coagulative hardening of the leather by chemicals

        Show answer
        Correct Option: D
        Explanation:

        Tanning is the process that converts the protein of the raw hide or skin into a stable material which will not putrefy and is suitable for a wide variety of end applications. The principal difference between raw hides and tanned hides is that raw hides dry out to form a hard inflexible material that can putrefy when re-wetted (wetted back), while tanned material dries out to a flexible form that does not become putrid when wetted back. A large number of different tanning methods and materials can be used. The choice is ultimately dependent on the end application of the leather. The most commonly used tanning material is chromium, which leaves the leather, once tanned, a pale blue colour (due to the chromium), this product is commonly called wet blue.

        Gelatin is often used as an ingredient in the manufacture of ice-cream. The reason for this is :

        chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

        1. to prevent the formation of a colloid.

        2. to stabilize the colloid and prevent crystal growth.

        3. to cause the mixture to solidify.

        4. to improve the flavour.

        Show answer
        Correct Option: B
        Explanation:

        Gelatin is a translucent, colourless, brittle (when dry), flavourless foodstuff derived from collagen obtained from various animal by-products. It is commonly used as a gelling agent in food, pharmaceuticals. Substances containing gelatin or functioning in a similar way are called gelatinous. Gelatin is an irreversibly hydrolyzed form of collagen. It is often used as an ingredient in the manufacture of ice-cream to stabilize the colloid and prevent crystal growth and works as protective colloid.

        Example of an intrinsic colloid is:

        chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

        1. $As _2S _3 sol$

        2. S sol

        3. Egg albumin

        4. $Fe(OH _2sol$

        Show answer
        Correct Option: C
        Explanation:

        Lyophilic or solvent loving : When dispersed phase has a greater affinity for the dispersion medium, the colloids are termed as lyophilic and when the dispersion medium is water, they are given the name hydrophilic. They are also called natural colloids, substances like proteins, starch, egg albumin and rubber etc. are grouped under this category.The lyophilic colloids are also called Intrinsic Colloids.

        Gelatin has the minimum protective powers.

        chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

        1. True

        2. False

        3. Ambiguous

        4. Data insufficient

        Show answer
        Correct Option: B
        Explanation:

        As we know,
        Smaller the gold number, higher the protective power of a colloid. Gold numbers of some protective colloids are given below :
        Protective Colloid                       Gold Number    
        Heamoglobin                                0.03 to 0.07        
        Starch                                              15 to 25      
        Gum Arabic                                      15 to 25        
        Gelatin                                            0.005 to 0.1
        so gelatin have maximum protective powers.

        Smoke precipitator works on the principle of :

        chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

        1. distribution law

        2. neutralization of charge on colloids

        3. Le-Chaterlier's principle

        4. addition of electrolytes

        Show answer
        Correct Option: B
        Explanation:

        Smoke precipitator works on the principle of neutralization of charge on colloids.
        Smoke coming out of the chimneys contain a lot of unburnt carbon particle. Smoke is the colloidalsolution of the solid particles such as carbon, arsenic, dust particles etc. These particles areinjurious to health and have to be precipitated . Carbon particle are charged particles and can notbe precipitated. Thus, a metal plate of oppositely charged particle is used for their precipitation. This is done bythe cottrell smoke precipitator which neutralizes the charge on the carbon particles and neutralizes them. In this way, smoke coming out of the chimneys gets free from the charged particles.

        Which of these can be one of the uses of colloids?

        chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

        1. Colloids act as transport vector

        2. Colloids are used in intravenous therapy

        3. Movement of enzyme molecules in water is because of colloid action

        4. All of the above

        Show answer
        Correct Option: D
        Explanation:

        Colloid acts as a transport vector of different contaminants in water surfaces. For example, heavy  metals and radionucleides are absorbed on colloid surface and are carried throughout the water
        Enzymes, which are important biomolecules in human body, freely move about in the water because of colloid action.
        Colloids are used in intravenous therapy where they increase the intravascular volume and maintain a high colloid osmotic pressure in the blood