Chemistry Test-29

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Chemistry Test-29

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Weekly Quiz Competition

Question 1
4 / -1

Which of the following does not give a silver mirror test with Tollen's reagent?

A
Sucrose

B
Glucose

C
Fructose

D
Lactose

Solution

Sucrosedoes not give a silver mirror test with Tollen's reagent.
Silver mirror test with Tollen's reagent is given by the molecule which contains an aldehyde group. But, sucrose has no aldehyde group and the rest of the molecule have an aldehyde group. Hence, glucose, fructose, and lactose, each gives a silver mirror test except sucrose.
Question 2
4 / -1

How many grams of \(\mathrm{CH}_3 \mathrm{OH}\) should be added to water to prepare \(150 \mathrm{ml}\) solution of \(2 \mathrm{M}~ \mathrm{CH}{ }_3 \mathrm{OH}\) ?

A
\(9.61 \times 10^3\)

B
\(2.4 \times 10^3\)

C
\(9.61\)

D
\(2.4\)

Solution

Given: \(150 \mathrm{ml}\) of \(2.0 \mathrm{M} ~\mathrm{CH}_3 \mathrm{OH}\) is to be prepared.
Number of moles \(=\mathrm{M} \times \mathrm{Volume ~in~ L}\) \(=2.0 \times 0.150=0.3\)
Molar mass of \(\mathrm{CH}_3 \mathrm{OH}=32.04 \mathrm{~g} / \mathrm{mol}\)
\(\therefore\) Weight of \(\mathrm{CH}_3 \mathrm{OH}\) to be added \(=32.04 \times 0.3=9.61 \mathrm{~g}\)
Question 3
4 / -1

Which of the following can not be predicted from an equilibrium constant for a reaction?

A
The extent of a reaction

B
which direction a reaction will proceed by measuring the concentrations of reactants and products

C
whether a system is at equilibrium by measuring the concentrations of the reactants and products

D
Nature of reactant and product

Solution

The correct option is 'Nature of reactant and product'.

Equilibrium constant for a reaction predict: the extent of a reaction; which direction a reaction will proceed by measuring the concentrations of reactants and products; whether a system is at equilibrium by measuring the concentrations of the reactants and products.

But it can not predict the nature of reactant or product.
Question 4
4 / -1

Current in an electrolyte is carried by ________.

A
only electrons

B
only -ve ions

C
only +ve ions

D
both +ve and -ve ions

Solution

In electrolytes, the charge carriers are ions, atoms that have gained electrons so they are negatively charged are called anions, and atoms that have lost electrons so they are positively charged are called cations. Thus, ions are charged particles (e.g. Na+ sodium ion or Cl- chloride ion in NaCl solution) and their movement or flow constitutes an electric current, i.e. the electrolyte consists of a stream of moving charged particles.
Hence, in electrolytes, the current is carried by both + ve and - ve ions.
Question 5
4 / -1

How much mass of \({ }^{235} U\) is required to undergo fission each day to provide \(3000 MW\) of thermal power? Average energy per fission is \(202.79 MeV\).

A
\(3.2 g\)

B
\(320 g\)

C
\(3.11 kg\)

D
\(32 kg\)

Solution

Power \(=3000 MW =3 \times 10^{9} \)joule/second
\(\therefore\) Energy to be produced each day
\(=3 \times 10^{9} \times 86400 \)joule each day
\(=2.592 \times 10^{14}\)jouleeach day
Energy per fission \(=202.79 MeV\)
\(=202.79 \times 10^{6} \times 1.6 \times 10^{-19} J =3.245 \times 10^{-11} \)joule
\(\therefore\) Number of Fissions each day
\(=\frac{2.592 \times 10^{14}}{3.245 \times 10^{-11}}=7.988 \times 10^{24}\) each day
\(0.235 kg\) of \({ }^{235} U\) contains \(6.02 \times 10^{23}\) atoms
\(\therefore M =\left(\frac{7.988 \times 10^{24}}{6.02 \times 10^{23}}\right)(0.235)=3.11 kg\)
Question 6
4 / -1

Given below are the half-cell reactions:
\(M n^{2+}+2 e^{-} \rightarrow M n ; E^{\circ}=-1.18 V\)
\(2\left(M n^{3+}+e^{-} \rightarrow M n^{2+}\right) ; E^{\circ}=+1.51 V\)
The \(E^{\circ}\) for \(3 \mathrm{Mn}^{2+} \rightarrow \mathrm{Mn}+2 \mathrm{Mn}^{3+}\) will be:

A
\(-0.33 V\): reaction will not occur

B
\(-0.33 V :\) reaction will occur

C
\(-2.69 V:\) reaction will not occur

D
\(-2.69 V:\) reaction will occur

Solution

Standard electrode potential of reaction will not change due to multiply the half-cell reactions with some numbers.
To get the main equation we have to reverse the given \(2 n d\) equation and add them,
So, \(E_{3}=E_{2}+E_{1}\)
\(E_{3}=-1.18+(-1.51)\)
\(E_{3}=-2.69 V\)
The reaction is not possible as the \(\Delta G\) will come +ve for this case and that indicates reaction is non-spontaneous.
Question 7
4 / -1

The gas given off when a metal reacts with an acid is:

A
hydrogen

B
oxygen

C
carbon dioxide

D
water vapour

Solution

Hydrogen gas is produced when a metal reacts with an acid. For example, when zinc reacts with hydrochloric acid, it produces zinc chloride and hydrogen gas.
Metal \(+\) Acid \(\rightarrow\) Salt \(+\) Hydrogen.
Question 8
4 / -1

Gibbs combined the first and the second laws of thermodynamics and gave a thermodynamic function 'G' which gets affected by
(a) The change in the enthalpy of the system.
(b) The change in the entropy of the system.
(c) The temperature of the system.

A
Only (a)

B
Only (b)

C
Both (a) and (b)

D
Only (c)

Solution

Gibb’s free energy is defined as ‘the energy associated with a chemical reaction that can be used to do work.’ The free energy (G) of a system is the sum of its enthalpy (H) minus the product of the temperature (T) and the entropy (S) of the system:
G = H - TS
Gibbs free energy combines the effect of both enthalpy and entropy. The change in free energy (ΔG) is equal to the sum of the change of enthalpy (∆H) minus the product of the temperature and the change of entropy (∆S) of the system.
∆G = ∆H - T∆S
*ΔG predicts the direction in which a chemical reaction will go under two conditions: (1) constant temperature and (2) constant pressure.
Question 9
4 / -1

In the hydroboration - oxidation reaction of propene with diborane, \(H _{2} O _{2}\) and \(NaOH\), the organic compound formed is:

A
\(CH _{3} CH _{2} CH _{2} OH\)

B
\(\left( CH _{3}\right)_{3} COH\)

C
\(CH _{3} CHOHCH _{3}\)

D
\(CH _{3} CHOHCH _{3}\)

Solution

The hydroboration-oxidation reaction is a two-step hydration reaction that converts an alkene into alcohol. It is an anti-Markovnikov reaction. The organic compound formed in the hydroboration - oxidation reaction of propene with diborane, \(H _{2} O _{2}\) and \(NaOH\) is \(CH _{3} CH _{2} CH _{2} OH\).
Question 10
4 / -1

The elements having the least number of electrons shells:

A
\(\mathrm{Li}\)

B
\(\mathrm{K}\)

C
\(\mathrm{Na}\)

D
\(\mathrm{Cs}\)
Solution
Lithium has the least number of electron shells. This is because of its position in the periodic table, which is higher than sodium and potassium.
Period of an element corresponds to the principal quantum number of the valence shell.
- \(\mathrm{Li}\) belongs to \( 2^{\text {nd }}\) period \(\quad 2\) electron shells
- \(\mathrm{Na}\) belongs to \(3^{\text {rd }}\) period \(\quad 3\) electron shells
- \(\mathrm{K}\) belongs to \( 4^{\text {th }}\) period \(\quad 4\) electron shells
- \(\mathrm{Cs}\) \) belongs to \( 5^{\text {th }}\) period \(\quad 5\) electron shells

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Chemistry Test-29

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Chemistry Test-29

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Question 1

Sucrose

Glucose

Fructose

Lactose

Solution

Question 2

\(9.61 \times 10^3\)

\(2.4 \times 10^3\)

\(9.61\)

\(2.4\)

Solution

Question 3

The extent of a reaction

which direction a reaction will proceed by measuring the concentrations of reactants and products

whether a system is at equilibrium by measuring the concentrations of the reactants and products

Nature of reactant and product

Solution

Question 4

only electrons

only -ve ions

only +ve ions

both +ve and -ve ions

Solution

Question 5

\(3.2 g\)

\(320 g\)

\(3.11 kg\)

\(32 kg\)

Solution

Question 6

\(-0.33 V\): reaction will not occur

\(-0.33 V :\) reaction will occur

\(-2.69 V:\) reaction will not occur

\(-2.69 V:\) reaction will occur

Solution

Question 7

hydrogen

oxygen

carbon dioxide

water vapour

Solution

Question 8

Only (a)

Only (b)

Both (a) and (b)

Only (c)

Solution

Question 9

\(CH _{3} CH _{2} CH _{2} OH\)

\(\left( CH _{3}\right)_{3} COH\)

\(CH _{3} CHOHCH _{3}\)

\(CH _{3} CHOHCH _{3}\)

Solution

Question 10

\(\mathrm{Li}\)

\(\mathrm{K}\)

\(\mathrm{Na}\)

\(\mathrm{Cs}\)

Solution

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