Chemistry Test 133

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Chemistry Test 133

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Weekly Quiz Competition

Question 1
4 / -1

Which of the following alkenes will react fastest with H₂ under catalytic hydrogenation conditions?

A

B

C

D

Solution

The reactivity order towards H₂ is

cis > iso > trans i.e in option A the alkene is cis.
Question 2
4 / -1

The heat of hydrogenation of 1-hexene is 126 When a second double bond is introduced in the molecule, the heat of hydrogenation of the resulting compound is 230 The resulting compound (diene) is

A
1, 3-Hexadiene

B
1, 4-Hexadience

C
1, 5-Hexadience

D
cannot predict from the given information

Solution

1,3 -hexadiene is a conjugated diene, hence it is more stable than the first compound. The heat of hydrogenation decreases as the stability of the molecule increases. The stability of 13 hexadiene is more than that of a compound which contain two double bonds.
Question 3
4 / -1

Heat of hydrogenation of benzene is 51 kcal/mol and its resonance energy is 36 kcal/mol. Then the heats of hydrogenation of cyclohexadiene and cyclohexene per mole respectively are

A
58 kcal, 58 kcal

B
25 kcal, 29 kcal

C
29 kcal, 58 kcal

D
58 kcal, 29 kcal

Solution

Total energy to break 3 bond in benzene is 87 [51+36].

So to break one bond i.e. in cyclohexaene is 87/3= 29 kcal/mol.

And to break 2 bond i.e.in cyclohexadiene is 29*2= 58 kcal/mole.
Question 4
4 / -1

H₂gas is liberated at cathode and anode both by electrolysis of the following aq. solution except in :

A
NaH

B
HCOONa

C
NaCl

D
LiH

Solution

At the cathode (C), water is reduced to hydroxide and hydrogen gas. The net process is the electrolysis of an aqueous solution of NaCl into industrially

Electrolysis of aqueous sodium chloride yields hydrogen and chlorine, with aqueous sodium. Chlorine gas bubbles out of the melt above the anode.
Question 5
4 / -1

“10 volume” H₂O₂ means :

A
1 mL H₂O₂ gives 10 mL O₂ at NTP

B
1 g H₂O₂ gives 10 mL O₂ at NTP

C
1 mol H₂O₂ gives 10 mL O₂ at NTP

D
none is correct

Solution

H₂O₂ is the special concentration terms.10 volume of H₂O₂means that 1ml of H₂O₂ gives 10 ml of O₂.

For example, if it was mentioned 30 volume of H₂O₂, then its means that 1ml of H₂O₂ gives 30ml of O₂.
Question 6
4 / -1

D₂O (heavy water) and H₂O differ in following except

A
freezing point

B
density

C
ionic product of water

D
its reaction with sodium

Solution

Chemical properties won't change in case of isotopes. Therefore answer is D.
Question 7
4 / -1

When 0.532 g of benzene (B.P. 80^o C) is burnt in a constant volume system with an excess of oxygen, 22.3 KJ of heat is given out. ∆H for the combustion process is given by :

A
–21 KJ

B
–1234.98 KJ

C
–221 KJ

D
–3273.26 KJ
Question 8
4 / -1

The work done by the system in a cyclic process involving one mole of an ideal monoatomic gas is 50 KJ/cycle, The heat absorbed by the system per cycle is

A
zero

B
50 KJ

C
–50 KJ

D
250 KJ

Solution

According to the first law of thermodynamics,

∆Q=∆U+∆W and for a cyclic process, change in internal energy(∆U) is zero. Hence ∆Q=∆W where ∆Q is the heat absorbed and ∆W is the work done. Therefore heat absorbed is 50 kJ
Question 9
4 / -1

Which of the following is not correct ?

A

B

C

D

Solution

It should be equal to T, not (-T)
Question 10
4 / -1

The heat released when NH₄OH & HCl neutralise is :

A
< 13.7 K. Cal.

B
> 13.7 K. Cal.

C
13.7 K. Cal.

D
None of these