Physical and chemical properties

What is the correct definition of liquefied gas according to IMO Gas Carrier Codes?

• A gas cooled or compressed to liquid phase, with vapour pressure 2.8 bars absolute or more at 37.8°C

• A gas compressed to a pressure below 1 bar at 37.8°C

• Any gas that is colourless and odourless

• A gas that is only cooled but not compressed

Which TWO statements about vapour density are correct?

• Vapour density compares the density of gas to air

• Gases with vapour density >1 rise and disperse easily

• Gases with vapour density <1 tend to sink and accumulate

• Gases with vapour density >1 tend to sink and may form explosive mixtures

Which statement about flash point is correct?

• Flash point is the highest temperature at which vapour is flammable

• Flash point is the lowest temperature at which enough vapour forms to create a flammable mixture

• Flash point is the temperature at which liquid boils

• Flash point has no relation to fire hazard

Which TWO factors affect the flammable limits of a gas mixture?

• Temperature of the mixture

• Colour of the gas

• Volume of the container

• Size of the ship

Which THREE substances or conditions can liquefied gas cargo react with?

• With itself

• With air

• With fresh water only

• With other materials

What is the correct description of polymerization?

• A reaction where small units (monomers) combine into large molecules (polymers)

• A reaction where polymers break into monomers

• A reaction that only happens under high pressure

• A type of decomposition reaction

What is the meaning of auto-ignition temperature?

• The temperature at which vapour forms a flammable mixture with air

• The boiling point of the cargo

• The temperature at which the liquid phase changes to gas

• The lowest temperature at which the product burns without external ignition

Which TWO statements about rollover are correct?

• It can occur when LNG layers of different densities mix suddenly
  

• It is not connected with pressure rise in a tank

• It results in rapid vapour release

• t happens when LPG cargo is loaded at ambient temperature

Which statement is true about saturated hydrocarbons?

• They have strong natural odour for leak detection

• They are colourless and odourless, mercaptan is added for detection

• They are always visible in case of leakage

• They naturally smell like sulphur

Which TWO statements describe properties of membrane tanks?

• Membrane tanks have thin primary barriers supported by insulation

• Membrane tanks are self-supporting structures

• Membrane tanks always have secondary barriers to ensure integrity

• Membrane tanks are designed to carry cargoes at ambient temperature