# Rocket Propulsion Questions and Answers – Liquid Oxidizers

This set of Rocket Propulsion Multiple Choice Questions & Answers (MCQs) focuses on “Liquid Oxidizers”.

1. __________ are not liquid oxidizers.
a) Nitrogen-fluorine formulations
b) Oxygen-fluorine compounds
c) Fluorinated hydrocarbons
d) Borohydrides

Explanation: Borohydrides are not liquid oxidizers. Rest of the options are storable, cryogenic liquid oxidizer propellants with high specific impulse values.

2. ___________ is a commonly used liquid oxidizer.
a) ClF3
b) OF2
c) ClF5
d) H2O2

Explanation: Hydrogen peroxide (H2O2) is a commonly used liquid oxidizer. But ClF2, OF2, ClF5, etc. are experimental liquid oxidizers.

3. LOX boils at _______ atmospheric pressure.
a) 909C
b) 90 K
c) 90 F
d) 90 R

Explanation: LOX refers to liquid oxygen. It boils at 90 K. Since their boiling point is very low, a cryogenic setup is required for the storage and transport of this oxidizer.

4. Which of the following is the specific gravity and heat of vaporization of LOX at atmospheric pressure?
a) 1.14; 213 kJ/kg
b) 1.08; 253 kJ/kg
c) 1.80; 235 kJ/kg
d) 1.41; 231 kJ/kg

Explanation: LOX refers to liquid oxygen. It has a specific gravity of 1.14. That means it is 1.14 times denser than water having a density of about 1000 kg/m3. It has a heat of vaporization of 213 kJ/kg.

5. What is the decrease in specific gravity of LOX if the tank pressure is increased from atmospheric pressure to 8 atm? (At 8 atm, specific gravity of LOX is 0.88)
a) 32.3%
b) 28.2 %
c) 22.8%
d) 25.3%

Explanation: The increase can be calculated using δinc = (δnew – δold) / δold x 100.
δinc=(0.88-1.14)/1.14 x 100 = -22.8. Hence the decrease is 22.8%.
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6. When are the tanks with cryogenic propellants pressurized?
a) Just before the engine start
b) After the engine start
c) 10 sec after the engine start
d) 10 sec before the engine start

Explanation: This is done to ensure that the propellants are at its lowest possible temperature. Else they might evaporate within the tank and may lead to devastating results under wrong circumstances.

7. Which of the following percentages of concentration of hydrogen peroxide is used for rocket applications?
a) 80 %
b) 60 %
c) 30 %
d) 10 %

Explanation: H2O2 used for rocket applications has a concentration of 80%. It is said to be in its highly concentrated form from 70% to 99%. For commercial uses, hydrogen peroxide is available at 30% concentration.

8. In the combustion chamber, hydrogen peroxide decomposes to give __________
a) hydrogen and oxygen
b) hydrogen and water
c) oxygen and water
d) water

Explanation: Decomposition of hydrogen peroxide gives oxygen and water.
The reaction is represented as H2O2 → H2O + 1/2O2 + heat.

9. Which of the following is not a catalyst used for H2O2 decomposition?
a) Platinum
b) Iron oxide
c) Manganese dioxide
d) Aluminium

Explanation: Aluminium tanks are generally used for storing H2O2 for this reason. Whereas hydrazine is not compatible with iron, copper, its alloys, monel, magnesium, zine or some types of aluminium alloys.

10. Theoretical specific impulse of 90% H2O2 is _______
a) 204 s
b) 154 s
c) 321 s
d) 114 s

Explanation: 90% H2O2 has a specific impulse of 204s. Because of this good specific impulse, countries like USA, Russia and Germany used concentrated hydrogen peroxide for monopropellant gas generation before 1955.

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