Heating and cooling of naphthalene

In the (a)   of naphthalene, the boiling tube containing the liquid naphthalene is cooled inside a conical flask

What is melting point of naphthalene

• 80.26 celcius

• 80.27 celcius

• 75.26 celcius

• 75.27 celcius

Diagram above shows the heating curve and naphthalene. Why the temperature remains constant along BC and DE?

• Heat energy is used to increase the kinetic energy of molecules.

• Heat energy is used to break the inter molecular forces between molecules

• Heat energy is lost to surrounding.

• Heat energy is used to build up the inter molecular forces between molecules

Diagram shows the cooling curve of naphthalene. At which stage the substance is in solid state and liquid simultaneously?

• MN

• NO

• OP

• MN and OP

Melting and freezing of naphthalene is occur at the same temperature.

• True

• False

What happens to naphthalene when heated?

• naphthalene rapidly sublimes directly from a solid into a gas

• naphthalene rapidly sublimes directly from a gas into a solid

• naphthalene slowly sublimes directly from a solid into a gas

• naphthalene slowly sublimes directly from a gas into a solid

What is the freezing point of naphthalene?

• 80.26 celcius

• 80.24 celcius

• 79.26 celcius

• 70.24 celcius

Why can naphthalene be heated directly?

• because to avoid of the direct heat of naphthalene

• to avoid the poisonous substances created

• because naphthalene can burn on its own easily

Why the naphthalene must be stirred continuously?

• to avoid supercooling

• to prevent ambient temperature from entering

• to avoid cooling

• to avoid melting

During the cooling of naphthalene, explain why :

The boiling tube must be placed in conical flask?

• To ensure an even cooling process

• To minimize the loss to surrounding

• To ensure an even melting process

• To avoid air from entering