Chemistry Test 83

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Chemistry Test 83

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Weekly Quiz Competition

Question 1
4 / -1

Which of the following expressions is correct between the van der Waals constant b and the radius r of spherical molecules?

A
b =

B
b = 2

C
b = 3

D
b = 4

Solution
Question 2
4 / -1

Which of the following polymers can be used for lubrication and as an insulator

A
SBR

B
PVC

C
PTFE

D
PAN

Solution

Teflon is used for lubrication and as an insulator, and because Polytetrafluoroethylene (PTFE) reduces friction and because of high resistivity it works as a good insulator too. Teflon is manufactured by heating tetrafluoroethene with a free radical or pursue catalyst at high pressures. It has high flexural strength, even in low temperature, high electrical resistance, and a low coefficient of friction.
Question 3
4 / -1

A
3.31 × 10¹¹ m ^-1

B
5.5 × 10¹⁰ m ^-1

C
5.51 × 10⁶ m ^-1

D
None of these

Solution
Question 4
4 / -1

When same amount of zinc is treated separately with excess of sulphuric acid and excess of sodium hydroxide solution, the ratio of volumes of hydrogen gas evolved is:

A
1: 1

B
1:2

C
2 : 1

D
9 : 4

Solution

The balanced chemical equation for the reaction of zinc with sulfuric acid is as shown below:

Zn+H₂SO₄→ZnSO₄+H₂( g)↑

1 mole of zinc reacts with 1 mole of sulfuric acid to produce 1 mole of hydrogen. The balanced chemical equation for the reaction of zinc with sodium hydroxide is as shown below:

Zn+2NaOH+2H₂O→Na₂[Zn(OH)₄]+H₂( g)↑

1 mole of zinc reacts with 2 moles of sodium hydroxide to produce 1 mole of hydrogen. Thus, the ratio of volumes of hydrogen evolved is 1:1.

Hence, the correct option is (A).
Question 5
4 / -1

The heat of reactions for the above reactions are Q,−11 and −9 respectively. What is Q?

A
-2

B
2

C
-20

D
-16

Solution
Question 6
4 / -1

In an ionic compound moles ratio of cation to anion is 1:2. If atomic masses of metal and non-metal respectively are 138 and 19, then correct statement is:

A
Molecular mass of compound is 176

B
Formula mass of compound is 176

C
Formula mass of compound is 157

D
Molecular mass of compound is 157

Solution

In an ionic compound mole ratio of cation to anion is 1:2 means empirical formula of an ionic solid contains 1 mole of cation & 2 moles of anion. Empirical formula represents the lowest whole number ratio of atoms in a molecule. The molecular formula is defined as the representation of the number of atoms present in a molecule. Metal forms the cation by donating electron & non-metal forms the anion by accepting an electron.

So, empirical formula mass of compound =1× atomic mass of metal +2× atomic mass of non − metal

=1 × 138 + 2 × 19

=176

Here, we can not calculate molecular mass as the molecular formula is not given in the question.

Hence, the correct option is (B).
Question 7
4 / -1

Arrange the following carboxylic acids in increasing order of reactivity towards thermal decarboxylation reaction:

A
I < III < II < IV

B
I < II < III < IV

C
I < IV < II < III

D
I < II < III < IV

Solution

The increasing order of reactivity towards thermal decarboxylation reaction for carboxylic acids is I<IV<II<III. Greater the stability of the carbanion intermediate, the greater the reactivity towards decarboxylation. III forms the most stable carbanion on the loss of CO₂ and I form the least stable carbanion. Carbanion from II is more stable than the carbanion from IV since −NO₂ is stronger electron-withdrawing group than C=O.

Hence, the correct option is (C).
Question 8
4 / -1

Amongst the following, the most basic oxides are:

A
CrO₂,MnO and BeO

B
Cr₂O₃,Fe₃O₄ and CeO

C
ZnO,TiO₂ and v₂O₅

D
CuO,FeO and NiO

Solution

Basicity is the property of a substance to donate unshared pair of electrons in water. It is based on electron pair availability, the more available the electrons, the more readily they can be donated therefore, the stronger will be the base.

The basicity decreases with increasing positive oxidation state. Low oxidation state means that some valence electrons of the metal atom are not involved in bonding. Therefore, the metal is not electron deficient. As a result, it can donate electrons and behave as a base. So, the most basic oxides will be,

CuO,FeO, and NiO

Hence, the correct option is (D).
Question 9
4 / -1

H₂ S contains 94.11% sulphur; SO₂ contains 50% oxygen and H₂O contains 11.11% hydrogen. Find the ratio of all given elements. After your calculations which law has been verified?

A
Law of multiple proportion is followed

B
Law of reciprocal proportion is followed

C
Law of conservation of mass is followed

D
All of the above

Solution
Question 10
4 / -1

An oxygen containing organic compound upon oxidation forms a carboxylic acid as the only organic product with its molecular mass higher by 14 units. The organic compound is:

A
A ketone

B
An aldehyde

C
A primary alcohol

D
A secondary alcohol

Solution

An oxygen containing organic compound upon oxidation forms a carboxylic as the only organic product with its molecular mass higher by 14 units. The organic compound is a primary alcohol. The primary alcohol is easily oxidized to carboxylic acid. The reaction is:

−CH₂−OH→−COOH

The net process is the addition of one O atom and removal of two H atoms. In the net process, the molecular mass increases by 14 units. The atomic masses of O and H are 16 g/mol and 1 g/mol respectively i.e., 16−2(1) =14

Secondary alcohol on oxidation gives ketone. When drastic conditions are used for the oxidation of ketone, the carbon skeleton breaks.

Hence, the correct option is (C).