# Applied Chemistry Questions and Answers – Viscosity and Viscosity Index – 1

This set of Applied Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Viscosity and Viscosity Index – 1”.

1. Viscosity means the flow of the liquid is resisted by ________
a) Itself
b) Other liquid
c) Water
d) Alcohol

Explanation: The viscosity of the liquid is defined as the resistance offered by the liquid for its own flow. The viscosity is more for the fluids having more density. The flow of one layer of the liquid is actually opposed by the other layer of the same liquid.

2. The viscosity of an oil decrease when temperature ________
a) Decreases
b) Is constant
c) Increases
d) 100oC

Explanation: The viscosity of an oil decreases with an increase of the temperature. In internal combustion engines and aeroplanes, the engine must start at low temperature and as well they must be operated at high temperatures. So, the viscosity of an oil must be moderate.

3. The rate of change of the viscosity with raise in temperature is measured by an arbitrary scale called as _________
a) Arbitrary constant
b) Viscosity constant
c) Viscosity index
d) Arbitrary index

Explanation: The rate of the change of the viscosity with raise in temperature is measured by an arbitrary scale called as viscosity index. The viscosity index is found by comparing the viscosity of the oil under the temperature of 1000F with two standard oils.

4. Mathematically, viscosity index can be given by __________
a) {(L+U)/(L-H)}*100
b) {(L -U)/(L+H)}*100
c) {(L+U)/(L+H)}*100
d) {(L -U)/(L-H)}*100

Explanation: The viscosity index can be given by {(L -U)/(L-H)}*100. Here, the U=viscosity at 100F oil under the test. V=viscosity at 100F of standard coast oil having V.I zero. H=viscosity at 100F of pennsylvanian crude oil having V.I 100

5. The viscosity of the oil changes rapidly with the change in temperature has _______
a) High V.I
b) Low V.I
c) Moderate V.I
d) Zero V.I

Explanation: The viscosity of some lubricating oils changes by the change in the temperature very rapidly. For such oils the V.I will be zero and for the viscosity of the oils which changes slightly with the change in temperature will have V.I high.
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6. Addition of linear polymers to the increases the V.I and oils with V.I higher than _______ are prepared.
a) 100
b) 1000
c) 10000
d) 100000

Explanation: Addition of the linear polymers to the increases the V.I and oils V.I higher than 100 are prepared. Generally, the viscosity is the only factor that decides the thickness of the oil or lubricating liquid.

7. If the viscosity must not be ________ to a liquid oil film between two moving liquid.
a) High
b) Low
c) Moderate
d) Zero

Explanation: The viscosity the most important and the only property of the lubricating oils to determine the thickness and velocity of the liquid. If the viscosity of an oil is too low then it is impossible to maintain liquid oil film between two moving or sliding liquids.so, every liquid must have good viscosity value.

8. Excessive friction takes place, when the viscosity is ________
a) Too high
b) Too low
c) Moderate
d) Zero

Explanation: The excessive friction takes place when the viscosity of the lubricating oil is too high. As the viscosity is too high then the layers of the sliding liquids will be moving fast and overlap on one another and causes the excess friction.

9. The viscosity of the lubricating oil must be sufficient to keep it in position.
a) True
b) False

Explanation: The viscosity of the lubricating must not be low. It also should not be too high. If it is too high then the liquid flow more faster and causes high or excessive friction. If it is low then the liquid moves very slowly and have low friction. Sufficient viscosity should be there to keep a liquid in a position.

10. ________ is used in machines operating at high pressure and slow speeds.
a) Kerosene
b) Diesel oil
c) Heavy oil
d) Crude oil

Explanation: Heavy oil is used as a lubricant in the machines that are operated at low speed under high pressure. The heavy oil is used as it has resist the squeezing between the rubbing parts while operating the machine.

11. For machines operating at the high speed and low pressure __________ are used.
a) Heavy oils
b) Light oils
c) Crude oils
d) Diesel oil

Explanation: For machines operating at the high speed and low pressure, the lubricating oil use is light oil. The light oil do not impose as much drag on high speed parts. Therefore, for the minimum friction, the thinner oil stays at position.

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