Chemistry Test 257

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Chemistry Test 257

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Weekly Quiz Competition

Question 1
4 / -1

Which of the following statements about H₃BO₃ is not correct ?

A
It is a strong tribasic acid

B
It is prepared by acidifying an aqueous solution of borax H₃BO₃ is a weak monobasic acid.

C
It has a layer structure in which planar BO₃ units are joined by hydrogen bonds

D
It does not act as proton donor but acts as a Lewis acid by accepting a lone pair of electrons

Solution

1. It is not a tribasic acid.

Option (a) is incorrect for H₃BO₃

2. Aqueous solution, instead of donating the −OH group it breaks the H−OH bond of water and accepts the −OH group from it leaving in the solution hence it is mono basic acid.
Question 2
4 / -1

A
r = k[OCl⁻][I⁻]

B
r = k[OCl⁻]²

C
r = k[I⁻]²[OCl⁻]

D
r = k[OCl⁻][I⁻]/[OH⁻]

Solution

On doubling the [OCl⁻] keeping the [I⁻] and [OH⁻] constant, the rate of formation of [OI⁻] is doubled, hence the order of reaction with respect to [OCl⁻] is one.

On doubling the [I⁻] keeping the [OCl⁻] and [OH⁻] constant, the rate of formation of [OI⁻] is doubled, hence the order of reaction with respect to I−is one.

On changing the [OH⁻] to a half-value, the rate of formation of [OI⁻] is doubled. Hence, the order of reaction with respect to [OH⁻] is −1.

Hence the rate law is r = k[OCl⁻] [I⁻] [OH⁻]⁻¹ = k[OCl⁻] [I⁻]/[OH⁻]
Question 3
4 / -1

The relative basic strength of the compounds is correctly shown in the option.

A
NH₂OH > NH₃> N₂H₄

B
N₂H₄> NH₂OH > NH₃

C
NH₃> N₂H₄ > NH₂OH

D
N₂H₄> NH₃> NH₂OH

Solution

In NH₃, the lone pair is completely available for donation, hence is most basic whereas NH₂− NH₂ and NH₂− OH can be considered as derivatives of NH₃. Here, H is replaced by −NH₂ forming NH₂− NH₂ and −OH forming NH₂− OH being highly electron withdrawing due to −O will decrease the election density most on −N.

∴ Least basic elect;on withdrawing −I-effect of

−NH₂ is less as compared to - OH.

Hence correct order of basic strength is

NH₃> NH₂− NH₂> NH₂− OH
Question 4
4 / -1

Dettol is a mixture of

A
chloroxylenol and terpeneol in a suitable solvent

B
formaldehyde and phenol in the solvent water

C
tincture of iodine and chloroform

D
KMnO₄ and iodoform
Solution
Dettol is an antiseptic solution composed of two main active ingredients: chloroxylenol and terpeneol. These ingredients are dissolved in a suitable solvent, such as ethanol or isopropyl alcohol.
- Chloroxylenol is effective against bacteria.
- Terpeneol contributes deodorant properties.
- The solvent aids in dissolving these components to create the liquid solution used for antiseptic purposes.
Question 5
4 / -1

In KO₂, the nature of oxygen species and the oxidation state of oxygen atom are (respectively)

A
Superoxide and -1

B
Oxide and -2

C
Peroxide and -1/2

D
Superoxide and -1/2

Solution

In KO₂, the nature of oxygen species and the oxidation state of oxygen atom are, superoxide and −1/2 respectively.

Superoxide ion is O^-₂.

Let X be an oxidation state of oxygen. The oxidation state of K is +1.

+ 1 + 2(X) = 0

2X = - 1

X = -1/2
Question 6
4 / -1

Consider separate solutions of 0.500 M C₂H₅OH (aq), 0.100 M Mg₃(PO₄)₂(aq), 0.250 M KBr (aq) and 0.125 M Na₃PO₄(aq) at 25^oC. Which statement is true about these solutions, assuming all salts to be strong electrolytes?

A
0.125 M Na₃PO₄(aq) has the highest osmotic pressure.

B
0.500 M C₂H₅OH (aq) has the highest osmotic pressure.

C
They all have the same osmotic pressure.

D
0.100 M Mg₃(PO₄)₂(aq) has the highest osmotic pressure.

Solution
Question 7
4 / -1

The concentrations of fluoride, lead, nitrate and iron in a water sample from an underground lake were found to be 1000 ppb, 40 ppb, 100 ppm and 0.2 ppm, respectively. This water is unsuitable for drinking due to high concentration of

A
Fluoride

B
Lead

C
Nitrate

D
Iron

Solution

Fluoride - 1000 ppb = 1 ppm (which is within the permitted levels, viz. < 10 ppm)

Lead - 40 ppb (which is within the permitted levels, viz. < 50 ppb)

Iron - 0.2 ppm( is the maximum permmiscible limit)

Nitrate - 100 ppm is not suitable for drinking.

[NO₃^-] > 50 ppm, in drinking water can cause disease such as methemoglobinemia ('blue baby' syndrome).
Question 8
4 / -1

The synthesis of alkyl fluorides is best accomplished by

A
Free radical fluorination

B
Sandmeyer's reaction

C
Finkelstein reaction

D
Swart's reaction

Solution
Question 9
4 / -1

The polymer obtained from the following reactions is:

A

B

C

D

Solution
Question 10
4 / -1

When 2-butyne is treated with H₂/Lindlar's catalyst, compound X is produced as the major product, and when treated with Na/liq. NH₃, it produces y as the major product. Which of the following statements is correct?

A
X will have higher dipole moment and higher boiling point than Y.

B
Y will have higher dipole moment and lower boiling point than X.

C
Y will have higher dipole moment and higher boiling point than X.

D
X will have lower dipole moment and lower boiling point than Y.

Solution

Dipole moment of X is more than Y.

Boiling point of X is more than Y.