Tag: chemistry

Questions Related to chemistry

State whether true or false :

Plastics are insoluble in water.

chemistry synthetic fibres and plastics environmental impact: plastics plastic plastic plastic waste garbage in, garbage out

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

 Plastics are high molecular weight (macromolecular or polymeric) organic substances that are synthesized from low molecular weight compounds. 


The organic monomers are hydrophobic in nature due to the presence of hydrocarbons and thus makes plastics water insoluble.


Example: polyethene- a polymer of ethylene.

Therefore, option A is correct.

Statement: Teflon doesn't stick to the materials and can be easily used in non-sticky pans and other cookware.
chemistry synthetic fibres and plastics environmental impact: plastics plastic plastic plastic waste garbage in, garbage out

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Teflon is a synthetic polymer of polytetrafluoroethylene that can be used to cover the surface of a certain object and imparts nonstick properties to it.  


Teflon is used for non-stick material because :


1. It is highly inert, i.e. doesn’t react with other substances easily.

2. It has a high melting point and shows exceptional electrical properties, which makes it an excellent choice to be used for the wiring of computer and aerospace applications.

3. Non-stick quality, which is why it’s used in numerous frying pans, pots, and other culinary tools.

Hence, the given statement is $\text{true}$.

Statement: Plastics which get deformed easily on heating and can be bent easily are known as thermoplastics.


State whether the given statement is true or false.

chemistry synthetic fibres and plastics environmental impact: plastics plastic plastic plastic waste garbage in, garbage out

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Plastics are categorized into thermosoftening/thermoplastic and thermosetting/thermoset plastics.


In thermosoftening/thermoplastic, the forces between the polymer chains are weak, so they can easily be remoulded into new shapes. 

This makes it possible to recycle this type of plastic. whereas in thermosetting plastics there are strong covalent bonds forming cross-links between the polymer chains, making these plastics hard and rigid. Once set into its original shape, a thermosetting plastic can't be softened and remoulded. 

The strong bonds between polymers also mean that thermosetting plastics are much more heat resistant than thermosoftening ones.

Hence, the given statement is $\text{true}$

Plastics are capable of molding and casting into various shapes and size plastic.

chemistry synthetic fibres and plastics environmental impact: plastics plastic plastic plastic waste garbage in, garbage out

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Plastics are categorized into thermosoftening and thermosetting plastics.
In thermosoftening plastics, the forces between the polymer chains are weak, so they can easily be remoulded into new shapes. This makes it possible to recycle this type of plastic. whereas in thermosetting plastics there are strong covalent bonds forming cross-links between the polymer chains, making these plastics hard and rigid. Once set into its original shape, a thermosetting plastic can't be softened and remoulded. The strong bonds between polymers also mean that thermosetting plastics are much more heat resistant than thermosoftening ones.
Example: Melamine is an example of a thermosetting plastic and polythene is a thermosoftening plastic.
Option A is correct

State whether true or false :

Bakelite is the first synthetic thermosetting plastics.

chemistry synthetic fibres and plastics environmental impact: plastics plastic plastic plastic waste garbage in, garbage out

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Bakelite is prepared in laboratories by controlling the pressure and temperature applied to phenol and formaldehyde. 


Baekeland produced a hard moldable material which he named "Bakelite". 

It was the first synthetic thermosetting plastic ever produced.

Therefore, option A is correct

When plastics are burnt toxic substances are released into the air causing water pollution.

chemistry synthetic fibres and plastics environmental impact: plastics plastic plastic plastic waste garbage in, garbage out

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

When plastics are burnt toxic substances are released into the air causing air pollution. Hence, the given statement is false.


Substances which cannot be decomposed by micro-organisms are called non-biodegradable substances.

chemistry synthetic fibres and plastics environmental impact: plastics plastic plastic plastic waste garbage in, garbage out

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Biodegradable substances are such materials which are and can be degraded by natural factors like microbes (e.g. bacteria, fungi and few more), abiotic elements like temperature, UV, oxygen, etc.
Unlike biodegradable, non-biodegradable substances like plastics, cannot be easily handled and cannot be decomposed or dissolved by natural agents.
Option A is correct

Plastics are eco-friendly.

chemistry synthetic fibres and plastics environmental impact: plastics plastic plastic plastic waste garbage in, garbage out

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

Plastics are human-made polymers and are non-biodegradable which means they cannot be easily handled and cannot be decomposed or dissolved by natural agents like microbes (e.g. bacteria, fungi), abiotic elements like temperature, UV, oxygen, etc. Thus are not eco-friendly.
Option B is correct

At equilibrium, the value of equilibrium constant $K$ is:

chemistry energetics and thermochemistry gibbs energy change and equilibrium gibbs free energy entropy and spontaneity

  1. $1$

  2. $2$

  3. $3$

  4. $0$

Show answer
Correct Option: A
Explanation:

At equilibrium $\Delta G=0$
$\Delta G=-nRT ln K$
$0=-nRT ln K$
or $K=1$

The equilibrium constants of a reaction is $73$. Calculate standard free energy change.

chemistry energetics and thermochemistry gibbs energy change and equilibrium gibbs free energy entropy and spontaneity

  1. $-106\ kJ\ mol^{-1}$

  2. $0.632\ kJ\ mol^{-1}$

  3. $60.32\ kJ\ mol^{-1}$

  4. $-10.632\ kJ\ mol^{-1}$

Show answer
Correct Option: D
Explanation:

${ \triangle G }^{ 0 }=-RTlnK$             $T={ 27 }^{ 0 }C=300K$

${ \triangle G }^{ 0 }=-8.3\times 300\times ln73$
          $=-10.632KJ{ mol }^{ -1 }$