Tag: chemistry

Questions Related to chemistry

What weight of sodium contains the same number of atoms as those in $8$ grams of oxygen?

chemistry the language of chemistry atomic weight and molecular weight masses of atoms and molecules chemical analysis and formulae

  1. $10.5 g$

  2. $13.5 g$

  3. $11.5 g$

  4. $14.2 g$

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Correct Option: C
Explanation:
Atomic weights of sodium and oxygen are 23 g/mol and 16 g/mol respectively.

8 g oxygen $ \displaystyle = \dfrac {8 \ g}{16 \ g/mol}= 0.5 \ $ moles of oxygen atoms.

Number of moles of sodium $ \displaystyle =$ number of moles of oxygen atoms $ \displaystyle = $ 0.5.

Weight of sodium $ \displaystyle = 0.5 \ mol \times 23 \ g/mol = 11.5 \ g$.

Note: Since sodium and oxygen samples have same number of atoms, they will have same number of moles.

What is the atomic mass of sodium?

chemistry the language of chemistry atomic weight and molecular weight masses of atoms and molecules chemical analysis and formulae

  1. $22\ g/mol$

  2. $23\ g/mol$

  3. $11\ g/mol$

  4. $20\ g/mol$

Show answer
Correct Option: B
Explanation:

A relative atomic mass is a measure of how heavy atoms are. It is the ratio of the average mass per atom of an element from a given sample to 1/12 the mass of a carbon-12 atom.

The relative atomic mass in 1 mole of isotopes of sodium atoms is 23 g/mol.

What is the relative atomic mass of cadmium?

chemistry the language of chemistry atomic weight and molecular weight masses of atoms and molecules chemical analysis and formulae

  1. 112.411 amu

  2. 20.00 amu

  3. 21.00 amu

  4. 20.43 amu

Show answer
Correct Option: A
Explanation:

The relative atomic mass is an average of the atomic masses of all the different isotopes in a sample, with each isotope's contribution to the average determined by how big a fraction of the sample it makes up.
The relative atomic mass of Cadmium is 112.411 amu.

Which of the following is/are correct?

chemistry the language of chemistry atomic weight and molecular weight masses of atoms and molecules chemical analysis and formulae

  1. One atomic mass unit is a mass unit equal to exactly one -twelfth (1/12th) the mass of one atom of carbon-12.

  2. One atomic mass unit is a mass unit equal to exactly one - sixteenth (1/16th) the mass of one atom of oxygen-16.

  3. The relative atomic mass of the atom of an element is defined as the average mass of the atom, as compared to 1/12h the mass of one carbon-12 atom.

  4. None of the above.

Show answer
Correct Option: A,B,C
Explanation:

The following are correct. One atomic mass unit is a mass unit equal to exactly one -twelfth (1/12th) the mass of one atom of carbon-12.
One atomic mass unit is a mass unit equal to exactly one - sixteenth (1/16th) the mass of one atom of oxygen-16.
The relative atomic mass of the atom of an element is defined as the average mass of the atom, as compared to 1/12h the mass of one carbon-12 atom.
For example, the mass of one carbon-12 atom is 12 amu. The mass of one magnesium-24 atom is 24 amu. The mass of one calcium-40 atom is 140 amu.

Oxygen occurs in nature as a mixture of isotopes $^16O$, $^17O$ and $^18O$ having atomic masses of 15.995 u, 16.999 u and 17.999 u and relative abundance of 99.763%, 0.037%, and 0.200% respectively. What is the average atomic mass of oxygen?

chemistry the language of chemistry atomic weight and molecular weight masses of atoms and molecules chemical analysis and formulae

  1. 15.999 u

  2. 16.999 u

  3. 17.999 u

  4. 18.999 u

Show answer
Correct Option: A
Explanation:
 Average atomic mass of an element existing in different isotopes is given by:
$M _{ avg }=\dfrac { \sum _{ i=1 }^{ n }{ { M } _{ i }{ A } _{ i } }  }{ \sum _{ i=1 }^{ n }{ A _{ i } }  } $
where $M _i=$atomic mass of an isotope with relative abundance of $A _i$
Given:$M _1=15.995 u,A _1=99.763,M _2=16.999 u, A _2=0.037,M _3= 17.999 u, A _3=0.200$
on subtitutiing we get:
${ M } _{ avg }=\dfrac { 15.995\times 99.763+16.999\times 0.037+17.999\times 0.200 }{ 99.763+0.037+0.200 } $
${ M } _{ avg }=15.999\ u$
option A is correct

For every ,one $^{37}Cl$ isotope there are three $^{35}Cl$ isotopes, in a sample of chlorine. What will be the average atomic mass of chlorine?

chemistry the language of chemistry atomic weight and molecular weight masses of atoms and molecules chemical analysis and formulae

  1. 35

  2. 37

  3. 35.5

  4. 35.6

Show answer
Correct Option: C
Explanation:
Average atomic mass of an element existing in different isotopes is given by:
$M _{ avg }=\dfrac { \sum _{ i=1 }^{ n }{ { M } _{ i }{ A } _{ i } }  }{ \sum _{ i=1 }^{ n }{ A _{ i } }  } $
where $M _i=$atomic mass of an isotope with relative abundance of $A _i$
Given:$M _1=37 u,A _1=1,M _2=35 u, A _2=3$
on subtitutiing we get:
${ M } _{ avg }=\dfrac { 37\times 1+35\times 3 }{ 1+3 } $
${ M } _{ avg }=35.5\ u$
option C is correct

One gm metal $M^{3+}$ was discharged by the passage of $1.81\times 10^{23}$ electrons. What is the atomic mass of metal?

chemistry the language of chemistry atomic weight and molecular weight masses of atoms and molecules chemical analysis and formulae

  1. $8g/mol$

  2. $9g/mol$

  3. $10g/mol$

  4. None of these

Show answer
Correct Option: C
Explanation:
Applying faraday's first law-
$ \dfrac{Q}{F} = \dfrac{Wt}{Mwt}\times V.f.$
$ \dfrac{ne}{F}= \dfrac{1}{Mwt}\times 3$
$  Mwt         = \dfrac{1\times F\times 3}{ne}$
$  Mwt         = 10\dfrac{gm}{mol}$

Which will not cause any atmospheric pollution?

chemistry natural resources- air, water and land environment and pollution environment pollution for a pollution free nature

  1. Hydrogen

  2. Sulphur dioxide

  3. Carbon dioxide

  4. Carbon monoxide

Show answer
Correct Option: A
Explanation:

Causes of Air pollution:
1. Burning of Fossil Fuels:
Sulfur dioxide emitted from the combustion of fossil fuels like coal, petroleum and other factory combustibles is one the major cause of air pollution. Carbon Monooxide caused by improper or incomplete combustion and generally emitted from vehicles is another major pollutant along with Nitrogen Oxides, that is produced from both natural and man made processes.
2. Agricultural activities: Ammonia is a very common by product from agriculture related activities and is one of the most hazardous gases in the atmosphere. Use of insecticides, pesticides and fertilizers in agricultural activities has grown quite a lot. They emit harmful chemicals into the air and can also cause water pollution.
3. Exhaust from factories and industries: Manufacturing industries release large amount of carbon monoxide, hydrocarbons, organic compounds, and chemicals into the air thereby depleting the quality of air. Manufacturing industries can be found at every corner of the earth and there is no area that has not been affected by it. Petroleum refineries also release hydrocarbons and various other chemicals that pollute the air and also cause land pollution.
4. Mining operations: Mining is a process wherein minerals below the earth are extracted using large equipments. During the process dust and chemicals are released in the air causing massive air pollution.
5. Indoor air pollution: Household cleaning products, painting supplies emit toxic chemicals in the air and cause air pollution.

The medium which is effected by a pollutants is called________.

chemistry air environment and pollution environment pollution for a pollution free nature

  1. receptor

  2. sink

  3. both $A$ and $B$

  4. system

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Correct Option: A
Explanation:

The medium which is effected by pollutants is called as receptor.
Hence option A is correct.

Natural source of pollution is:

chemistry air environment and pollution environment pollution for a pollution free nature

  1. rain forest

  2. mining of minerals

  3. forest fire

  4. falling of meteoroids

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Correct Option: C
Explanation:

Forest fires are one of the main natural sources of pollution. The forests catch fire due to high temperature in summers