Chemistry Test 189

Result

Chemistry Test 189

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Weekly Quiz Competition

Question 1
4 / -1

If the anions (A) form hexagonal close packing and cations (B) occupy only 2/3^rd octahedral voids in it, then the general formula of the compound is :

A
AB

B
A₃B₂

C
A₂B

D
AB₂

Solution

No of octahedral voids in hcp = 6 so formula A₆B₄ = A₃B₂.
Question 2
4 / -1

In an ionic solid r₍₊₎ = 1.6 Å and r₍₊₎ = 1.864 Å. Use the radius ratio rule to determine the edge length of the cubic unit cell in Å.

A
4

B
2√3

C
3√3

D

Solution
Question 3
4 / -1

Three lines are drawn from a single corner of an FCC unit cell to meet the other corner such that they are found to pass through exactly only 1 octahedral void, no voids of any type and exactly 2 tetrahedral voids with 1 octahedral void. Identify the line in the same order.

A
Edge, Face diagonal, Body diagonal

B
Face diagonal, Edge, Body diagonal

C
Body diagonal, Face diagonal, Edge

D
Edge, Body diagonal, Face diagonal

Solution
Question 4
4 / -1

Platinum crystallises in a face centered cube crystal with a unit cell length of 3.9231 Å. The density and atomic radius of platinum are respectively. [Atomic mass of Pt = 195]

A
45.25 g. cm^–3, 2.516 Å

B
21.86 g. cm^–3, 1.387 Å

C
29.46 g. cm^–3, 1.48 Å

D
None of these

Solution
Question 5
4 / -1

A 0.2 molal aqueous solution of a weak acid (HX) is 20 percent ionised. The freezing point of this solution is (Given k_f = 1.86º C kg mol^–1 for water) :

A
–0.45ºC

B
– 0.90ºC

C
–0.31 ºC

D
– 0.53ºC

Solution

ΔT_f = 0.2 x 1.2 x 1.86 = 0.45 therefore freezing point = – 0.45°C
Question 6
4 / -1

The vapour pressure of the solution of two liquids A(pº = 80 mm) and B(pº = 120 mm) is found to be 100 mm when x_A = 0.4. The result shows that :

A
solution exhibits ideal behaviour

B
solution shows positive deviation

C
solution shows negative deviation

D
solution will show positive deviation for lower concentration and negative deviation for higher concentrations

Solution

P_Total = 0.4 x 80 + 0.6 x 120 = 104 > 100 mm of Hg

Experimental P_total is lower then ideal P_total, So solution shows negative deviation.
Question 7
4 / -1

A 0.004 M solution of Na₂SO₄ is isotonic with 0.010 M solution of glucose at same temperature. The apparent percentage dissociation of Na₂SO₄ is :

A
25%

B
50%

C
75%

D
85%

Solution
Question 8
4 / -1

Consider equimolal aqueous solutions of NaHSO₄ and NaCI with ΔT_b and ΔT'_b as their respective boiling point elevations. The value of

A
1

B
1.5

C
3.5

D
2/3

Solution

As m → 0 (infinite dilution) both electrolytes will be completely dissociated so
Question 9
4 / -1

The reduction potential of hydrogen half cell will be negative if (T = 298 K) :

A

B

C

D

Solution
Question 10
4 / -1

Aqueous solution of Na₂SO₄ containing a small amount of Phenolphthalein is electrolysed using Pt-electrodes. The colour of the solution after some time will

A
remain colourless

B
change from pink to colourless

C
change from colourless to pink

D
remain pink

Solution

Remains colourless since solution is acidic and Phenolphthalein shows pink colour only in basic medium.