# Chemical Engineering Questions and Answers – Specific Gravity

This set of Basic Chemical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Specific Gravity”.

1. What is the unit of specific gravity?
a) Kg/m3
b) N/m3
c) m/s2
d) Dimensionless

Explanation: Specific gravity of a substance is the ratio of density of the substance and density of a reference substance, so it is dimensionless.

2. What is the specific gravity of a substance with density 100 kg/m3 with respect to reference substance of density 100 lb/m3?
a) 1.1
b) 2.2
c) 3.3
d) 4.4

Explanation: Density of the substance = 100*2.2 = 220 lb/m3, Specific gravity = (100*2.2)/100 = 2.2.

3. It is necessary to mention the temperature at which specific gravity is calculated, because
a) Mass of the substance changes with temperature
b) Rigidity of the substance changes with temperature
c) Density of the substance changes with temperature
d) None of the mentioned

Explanation: Since the volume of the substance changes with temperature, which means density of the substance changes with temperature, that’s why it is required to mention the temperature at which specific gravity is calculated.

4. What is the specific gravity of a substance with mass 10 kg and volume 2 m3, with respect to the reference density 50 kg/m3?
a) 0.1
b) 0.2
c) 0.3
d) 0.4

Explanation: Density of the substance = 10/2 = 5 kg/m3, => Specific gravity = 5/50 = 0.1.

5. What is the mass of a cone of radius 1 m and height 3 m having specific gravity 0.1? (Density of water = 1000 kg/m3)
a) 314.16 kg
b) 425.24 kg
c) 136.16 kg
d) 325.24 kg

Explanation: Volume of cone = (1/3) π12*3 = 3.1416 m3, density of cone = 0.1*1000 = 100 kg/m3, => mass of cone = 100*3.1416 = 314.16 kg.
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6. API gravity is measured in,
a) Gravity meter scale
b) Hydrometer scale
c) Richer scale
d) None of the mentioned

Explanation: API gravity is measured in Hydrometer scale.

7. API gravity is necessary for the calculation of specific gravity of petroleum products, because
a) Volume of the petroleum products changes with temperature
b) Mass of petroleum products changes with temperature
c) Potential energy of petroleum products changes with temperature
d) None of the mentioned

Explanation: Since volume of petroleum products changes significantly with temperature, that means density of petroleum products changes significantly with temperature, so that’s why specific gravity of petroleum products changes with temperature, and that’s why API gravity is required.

8. What is the API gravity of a substance with specific gravity 1?
a) 131.5
b) 141.5
c) 10
d) 50

Explanation: API = (141.5/sp.gr) – 131.5 = 141.5/1 – 131.5 = 10.

9. What is the average mass of a substance with specific gravity 10, and its volume varies with time as V = t/500, from t = 2, to t = 0 seconds? (Density of water = 1000 kg/m3)
a) 25
b) 20
c) 40
d) 75

Explanation: Density of substance = 10 * 1000 = 10000 kg/m3, => mass of substance = 10000*t/500 = 20t, => average mass = (1/2)∫20t = 5t2 = 5(22 – 02) = 20.

10. Mass of a substance is changing with respect to its volume as m = -v3 + 3v2 -2v, what is the maximum specific gravity of the substance between v = 1 m3 and v = 2 m3? (Density of reference substance = 0.25 kg/m3)
a) 1
b) 2
c) 3
d) 4

Explanation: Density of substance D = m/v = -v2 + 3v – 2, => Specific gravity of substance S = D/0.25 = 4(-v2 + 3v – 2), => dS/dv = 4(-2v + 3) = 0, => v = 1.5, => S is maximum at v = 1.5, => maximum specific gravity = 4(-1.52 + 3*1.5 – 2) = 1.

11. What is the specific gravity of 10 Kg of water occupied in 10 m3 with respect to 200 g/m3?
a) 0.2
b) 0.5
c) 1
d) 5

Explanation: Specific gravity = (10/10)/0.2 = 5.

12. What is the specific gravity of 5 Kg of water occupied in 10 m3 with respect to 500 g/m3?
a) 0.5
b) 1
c) 2
d) 5

Explanation: Specific gravity = (5/10)/0.5 = 1.

13. What is the specific gravity of 10 Kg of water occupied in 5 m3 with respect to 100 g/m3?
a) 1
b) 5
c) 10
d) 20

Explanation: Specific gravity = (10/5)/0.1 = 20.

14. What is the specific gravity of O2 at 27oC and 60 Pa with respect to 1 Kg/m3?
a) 0.15
b) 0.28
c) 0.54
d) 0.76

Explanation: Specific gravity = (60*32/8.314*300)/1 = 0.76.

15. What is the specific gravity of N2 at 27oC and 6 Pa with respect to 0.1 Kg/m3?
a) 0.16
b) 0.33
c) 0.51
d) 0.89

Explanation: Specific gravity = (6*14/8.314*300)/0.1 = 0.33.

Sanfoundry Global Education & Learning Series – Basic Chemical Engineering.

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