TS EAMCET 2019 :: Chemistry :: General questions

• Chemistry - General questions

The mass of haemoglobin in mg required to protect from coagulation of 50mL of a gold sol on adding 5mL of 10% NaCl solution is (gold number of haemoglobin=0.03)

Answer:

Explanation:

Gold number is the number of milligrams of the protective colloid which prevents the coagulation of 10mL of red gold solution. When 1 mL of a 10 per cent solution of sodium chloride is added to it. Here, gold number of Hb=0.03. So the mass of Hb require for 10 mL of gold is 0.03 mg. So, weight (mass) requires for 50mL of gold solution is 0.15 mg

How many grams of glucose are required to prepare an aqueous solution of glucose having a vapour pressure of 23.324 mm Hg at $25^{0} C $ in 100 g of water? The vapour pressure of pure water at $25^{0}C$ is 23.8 mmHg.

(Molar mass of glucose =180 g mol^-1) 

Answer:

Explanation:

Vapour pressure of pure solvent

 = $p^{0}$=23.8 mm of Hg

 Vapour pressure of solution  (p0) =23.324 mm of Hg

Thus, difference in vapour pressure($\triangle$p)

=23.8-23.324=0.476mm of Hg

$\because$        $\frac{\triangle p}{p^{0}}=\frac{w_{B}}{M_{B}} \times  \frac{M_{A}}{w_{A}}$   (for dilute solution)

where, M_A and w_A are molar mass and actual mass of solvent respectively

 M_B and w_B are molar mass and actual mass of solute respectively;

Given;

 M_A=18, w_A=100

w_B=M_B=180

$w_{B}=\frac{\triangle p \times M_{B} \times w_{A}}{p^{0} \times M_{A}}$

   =$=\frac{0.02 \times180\times100}{18}$       $\left[\frac{\triangle p}{p^{0}}=\frac{0.476}{23.8}=0.02\right]$ 

  =20.00

Hence, option (a) is the correct answer      

The boiling point (in K) of cis but-2-ene and dipole moment (in D) of trans but-2-ene  are respectively

Answer:

Explanation:

Boiling point =$37^{0}C(\approx$277k)

$\mu=0.33D$

 cis-but-2ene has higher dipole-dipole attraction than trans-isomer hence, has high boiling point.

Boiling point=0.9= ° C( $\approx$ 274 K)

 $\mu=0D$

  the dipole moment of trans-but-2ene is zero because the bond dipoles cancel each other.

However, the dipole moment of cis-but-2-ene  is 0.33 D , the vector  sum of the two bond dipoles

Match the following

THe correct statement is 

Answer:

Explanation:

 A-II,B-I,C-IV,D-III

 (A) , $SO_{2}$  Acid rain is caused by chemical reaction that begins when compounds like sulphur dioxide and nitrogen oxides are released into the air. There amount can rise very high into the atmosphere, where they mix and react with water , oxygen and other chemicals to form more acidic pollutants, known as acid rain

(B)  Photochemical smog is a mixture of air pollutants that have been chemically altered into further noxious compounds by exposure to sunlight. The main compounds of photochemical smog  are nitrogen oxides, volatile organic  compounds, tropospheric ozone and PAN(peroxy Acetyl nitrate)

(C)  Smoke  smoke  is a collection of  airborne solid and liquid particulates and gases emitted when a material undergoes combustion

(D)  $CF_{2}Cl_{2}, CFCs$ (chlorofluorocarbons ), oxides of nitogen are startospheric pollutants.

What are two types of crystal structures shown by ice at different pressures?

Answer:

Explanation:

 Ice can assume a larger number of different crystalline structures, more than any other known material. At ordinary pressure, the stable phase of ice is called ice  1. There are two closely related variants of ice 1: hexagonal ice  I_h, which has hexagonal symmetry and cubic ice I_c, which has a crystal structure similar to diamond.

Ice I_h is the normal form of ice; ice I_c is formed by depositing  vapour at very low temperatures (below 140 K)

• Chemistry - General questions