1
Q:

# Dust particles in the air of large industrial cities are removed by

 A) Sedimentation B) Electrophoresis C) Tyndall effect D) Brownian movement

Explanation:

Dust particles such as coal dust(smoke) are fine particle of a solid (carbon in the case of smoke) dispersed in air. They are colloidal systems and the particles are charged either positive or negative. In an applied electrical field, they are attracted towards the opposite electrodes. Movement of the particles towards the electrodes is known as 'electrophoresis'. Hence electrophoresis is applied to remove smoke within the chimeny itself without allowing it to escape into the air and cause nuisance.

Subject: Chemistry
Q:

SI unit of equivalent conductance

 A) ohm/cm B) Siemens m2/equivalent C) Siemens/equivalent D) mho/cm

Explanation:

Equivalent conductance is defined as the conductance of an electrolyte solution containing one gram equivalent of the electrolyte. It is equal to the product of specific conductance (k) of the solution and the volume (V) of the solution that contains one gram equivalent of the electrolyte.

$\lambda$ = k x V

Unit of spceific conductance k is Siemens / m.

Volume of the solution V is ${\mathbf{m}}^{\mathbf{3}}$

Now, required equivalent conductance unit is .

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1 32
Q:

what is the gram formula mass of ${\left({\mathbf{NH}}_{\mathbf{4}}\right)}_{\mathbf{3}}{\mathbf{PO}}_{\mathbf{4}}$?

 A) 139.54 B) 140.70 C) 149.08 D) 153.24

Explanation:

The gram formula mass is nothing but molar mass.

Composition :

Symbol      Element       Atomic weight       Atoms

P         Phosphorus       30.973762               1       = 30.973

O         Oxygen             15.9994                  4       =  63.998

N         Nitrogen            14.0067                  3       =  42.020

H         Hydrogen          1.00794                  12      =  12.096

Total   =  30.973+63.998+42.020+12.096 = 149.087

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0 55
Q:

Proteins differ from one another because

 A) The peptide bonds linking amino acids differ from protein to protein B) Each protein contains its own unique sequence of sugar molecules C) The number of nucleotides found in each protein varies from molecule to molecule D) The sequence of amino acids in the polypeptide chain differs from protein to protein

Answer & Explanation Answer: D) The sequence of amino acids in the polypeptide chain differs from protein to protein

Explanation:

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0 26
Q:

Formation of curd from milk is chemical reaction.

 A) TRUE B) FALSE

Explanation:

Milk is converted into curd or yogurt by the process of fermentation. Milk consists of globular proteins called casein.

It is biochemical change because here microorganism named lactobacillus react with milk and turn it to curd. Lactobacillus required favourable condition to grow.

For it 37 degree temperature is needed. But sometimes when it does not get favourable condition, then other microorganism react and makes the curd taste different.

Subject: Chemistry
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1 49
Q:

Which type of molecule is CF4?

 A) nonpolar, with a symmetrical distribution of charge B) polar, with an asymmetrical distribution of charge C) nonpolar, with an asymmetrical distribution of charge D) polar, with a symmetrical distribution of charge

Answer & Explanation Answer: A) nonpolar, with a symmetrical distribution of charge

Explanation:

CF4 is tetrahedral.

Since the four 'F' atoms have the same electronegativity values, there is no bias in electron distribution toward any one.

Therefore, electron/charge distribution is symmetrical, which also means that the molecule is nonpolar.

Hence, CF4 is nonpolar molecule with a symmetrical distribution of charge.

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1 36
Q:

Which structural formula represents a dipole?

 A) 4 B) 3 C) 2 D) 1

Explanation:

What is Dipole :

when two atoms in a molecule have substantially different electronegativity: One atom attracts electrons more than another, becoming more negative, while the other atom becomes more positive.

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1 77
Q:

Which of the following elements is a metal?

 A) Se B) I C) Zn D) S

Explanation:

In chemistry, a metal is an element that readily forms positive ions (cations) and has metallic bonds. Metals are opaque, lustrous elements that are good conductors of heat and electricity. Most metals are malleable and ductile and are, in general, denser than the other elemental substances.

Examples of metals are aluminium, copper, iron, tin, gold, lead, silver, titanium, uranium, and zinc.

Here Se - Selenium is an element but is not a metal, S - Sulphur is not a metal and I - Iodine is also not a metal.

Hence, Zn - Zinc is the only metal in the given options.

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4 60
Q:

What is the gram formula mass of ${\mathbf{Li}}_{\mathbf{2}}{\mathbf{SO}}_{\mathbf{4}}$?

 A) 101.2487 B) 109.9446 C) 111.2687 D) 106.5871

Explanation:

The term gram formula mass is synonymous with molecular mass. So, to get this, we must add molar mass of all the elements in this compound.

Given compound is Lithium Sulphate - ${\mathbf{Li}}_{\mathbf{2}}{\mathbf{SO}}_{\mathbf{4}}$

Elemental calculation ::

Li  -  Lithium   -   6.941    -     2   -   13.88200 %
S  -  Sulfur     -    32.065   -    1   -   32.065 %
O  -  Oxygen   -   15.9994  -    4   -   63.9976 %

Now, total = 12.6264 + 29.1647 + 58.2090 = 109.9446

Hence, the gram formula mass of Li2SO4 = 109.9446.