Tag: applied chemistry

Questions Related to applied chemistry

Which of the following statement(s) is true?

nanochemistry nanotechnology applied chemistry materials chemistry

  1. Nanomaterials have different colours than the bulk material.

  2. Gold nanoparticles are red.

  3. Bulk gold metal is yellow.

  4. All of the above

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Correct Option: D
Explanation:

All of the given statements are true. Nano materials have different colours than the bulk material. Gold nano particles are red. Bulk gold metal is yellow.

Nanoparticles are the nanomaterials with ____ dimension(s) between 1 nm and 100 nm.

nanochemistry nanotechnology applied chemistry materials chemistry

  1. one

  2. two

  3. three

  4. either one or two

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Correct Option: C
Explanation:

Nanoparticles are the nanomaterials with three dimension between 1 nm and 100 nm. Nanolayers are the nanomaterials with only one dimension between 1 nm and 100 nm. Nanotubes or nanowires are the nanomaterials with two dimension between 1 nm and 100 nm.

Which of the following is/are true?

nanochemistry nanotechnology applied chemistry materials chemistry

  1. The nanoparticles have substantial percentage of atoms on the surface and are therefore bound less tightly than those within the bulk solid.

  2. The nanomaterials have lower melting points than the bulk material.

  3. The nanomaterials tend to have greater reactivity than the bulk material.

  4. All of the above.

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Correct Option: D
Explanation:

All of the given statements are true.
The nanoparticles have substantial percentage of atoms on the surface and are therefore bound less tightly than those within the bulk solid. For example, a 5 nm nanoparticle has about 30%  of the atoms on its surface. This property of nanoparticles is responsible for the lower melting point and greater reactivity of nanomaterials than the bulk solid.

1 nm is the width of __________ hydrogen atoms placed side by side.

nanochemistry nanotechnology applied chemistry materials chemistry

  1. 2

  2. 4

  3. 10

  4. 50

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Correct Option: B
Explanation:

1 nm is the width of 4 hydrogen atoms placed side by side.

The size of nano materials lies between the width of ______ hydrogen atoms laid side by side.

nanochemistry nanotechnology applied chemistry materials chemistry

  1. 1-5

  2. 4-25

  3. 100-150

  4. 1000-5000

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Correct Option: B
Explanation:

The size of nanomaterials lies between the width of 4-25 hydrogen atoms laid side by side. 1 nm is the width of 4 hydrogen atoms placed side by side. Nanomaterials have atleast one dimension between 1 nm and 100 nm.

Which of the following is true?

nanochemistry nanotechnology applied chemistry materials chemistry

  1. The nanomaterials tend to have greater reactivity than the bulk material.

  2. The nanomaterials tend to have lower reactivity than the bulk material.

  3. The nanomaterials tend to have same reactivity as the bulk material.

  4. There is no generalisation between reactivity of nanomaterial and bulk material.

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Correct Option: A
Explanation:

The nanomaterials tend to have greater reactivity than the bulk material. For example, gold nanoparticles are chemically reactive whereas bulk metal is inert.

Which of the following is true?

nanochemistry nanotechnology applied chemistry materials chemistry

  1. The nanomaterials have lower melting points than the bulk material.

  2. The nanomaterials have higher melting points than the bulk material.

  3. The nanomaterials have approximately same melting points as the bulk material.

  4. The nanomaterials can have either lower or higher ( but not equal) melting points than the bulk material.

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Correct Option: A
Explanation:

The nano materials have lower melting points than the bulk material.

Which of the following is / are true?

nanochemistry nanotechnology applied chemistry materials chemistry

  1. When a quantum dot is irradiated with UV light, it emits visible light, the wavelength of which depends on the size of nanoparticles.

  2. The rainbow colours are emitted by the nanoparticles of different size of single substance.

  3. The wavelength of light emitted decreases from red to violet in the rainbow spectrum as the size of the nanoparticles decreases.

  4. All of the above.

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Correct Option: D
Explanation:

All of the given statements are correct.
When a quantum dot is irradiated with UV light, it emits visible light, the wavelength of which depends on the size of nanoparticles. For example, a 3nm cadmium selenide particle emits green light of wavelength 520 nm whereas 5.5 nm particle of the same substance emits red light at the wavelength of 620 nm.
The rainbow colours are emitted by the nanoparticles of different size of single substance.
The wavelength of light emitted decreases from red to violet in the rainbow spectrum as the size of the nanoparticles decreases.

The size of a nano particle is  about _________ times smaller than the diameter of a single strand of human hair.

nanochemistry nanotechnology applied chemistry materials chemistry

  1. 10

  2. 100

  3. 1000

  4. 50000

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Correct Option: D
Explanation:

The size of a nanoparticle is  about 50000 times smaller than the diameter of a single strand of human hair and 1/100th of a typical bacterium.

____________ nanotubes are used as strengthening rods and toughening elements in structural composite materials.

nanochemistry nanotechnology applied chemistry materials chemistry

  1. Carbon

  2. Gold

  3. Silver

  4. Metal oxide

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Correct Option: A
Explanation:

Carbon nanotubes are used as strengthening rods and toughening elements in structural composite materials. Example of a carbon nanotube is Fullerene nanotube.