Tag: discovery of subatomic particles

Questions Related to discovery of subatomic particles

Select the correct statement?

chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

  1. An atom has equal number of electrons and protons.

  2. An atom has equal number of electrons and neutrons.

  3. An atom has equal number of protons and neutrons.

  4. An atom has equal number of electrons, protons and neutrons.

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Correct Option: A
Explanation:

An atom is electrically neutral as it has an equal number of electrons and protons, that is, an equal number of negative and positive charges. 


In order to become stable, atom loses or gains one or more electrons and forms an ion which carries a charge.

Hence the correct option is A.

What is the total number of electrons present in 1.6 g of methane?

chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

  1. $6.023 \times 10^{23}$

  2. 16

  3. $12.04 \times 10^{23}$

  4. $6.023 \times 10^{24}$

Show answer
Correct Option: A
Explanation:
1 mole methane = 16 g
Electrons in 1 mole of methane are $=6+4 \times 1=10$
Mole of methane in 1.6 g=$\cfrac{mass}{molar\ mass}$
$=\cfrac{1.6}{16}=0.1$ mole
$\therefore$ 0.1 mol methane contains $0.1 \times 10$mol electron=1 mole of electron
1 mole electron=$6.023 \times 10^{23}$ electrons

The molar mass of an electron is:

chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

  1. $6.023\times10^{23}$ g/mol

  2. $5.486\times10^{-4}$ g/mol

  3. $9.108\times10^{-28}$ kg/mol

  4. $9.108\times10^{-24}$ g/mol

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Correct Option: B
Explanation:

Mass of an electron $=9.1\times 10^{-28}$g
1 mole $=6.02\times 10^{23}$ electrons
$\therefore$ molar mass of electron $=(9.1\times 10^{-28}) \times (6.02\times 10^{23}) = 5.48\times 10^{-4}$ g/mole

The total number of electrons present in 1.8 g of water is :

chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

  1. $6.023\times 10^{22}$

  2. $10.8576\times 10^{23}$

  3. $10.8576\times 10^{22}$

  4. $6.023\times 10^{23}$

Show answer
Correct Option: D
Explanation:

We know that, 1 molecule of water consists of 10 electrons (2 electrons each of two hydrogen atoms and 8 electrons of one oxygen atom).
The number of molecules present in 1.8 g of water.
$18 : g : of : H _2O\xrightarrow[]{contains}6.023\times 10^{23}molecules$
$\Rightarrow1.8 : g : of : H _2O : contains : '! x' : molecules$
$x=\dfrac{1.8\times 6.023\times 10^{23}}{18}$
$=\dfrac{ 6.023\times 10^{23}}{10}=6.023\times 10^{22}molecules$.
$\therefore$ Number of electrons in 1.8 g of water $=6.023\times 10^{22}\times10=6.023\times 10^{23}$

How many moles of electron weighs one kilogram?

chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

  1. $6.023\times 10^{23}$

  2. $\dfrac {1}{9.108}\times 10^{31}$

  3. $\dfrac {6.023}{9.108}\times 10^{54}$

  4. $\dfrac {1}{9.108\times 6.023}\times 10^8$

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Correct Option: D
Explanation:

Mass of one electron is $9.108\times 10^{-31} kg$.


Mass of one mole of electrons is ${9.108 \times 10^{-31} \times 6.023}\times 10^{23}={9.108\times 6.023}\times 10^{-8}$.

Thus, $1$ kg corresponds to $\dfrac {1}{9.108\times 6.023}\times 10^8$ moles of electrons.

Hence, the correct option is $D$

How many moles of electrons weigh one kilogram? 

(Mass of electron = $\displaystyle 9.108\times 10^{-31}kg $; Avagadro number = $\displaystyle 6.023\times 10^{23}kg $)

chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

  1. $\displaystyle \frac{1}{9.108\times 6.023}\times 10^{8} $

  2. $\displaystyle 6.023\times 10^{23}$

  3. $\displaystyle \frac{1}{9.108}\times 10^{31}$

  4. $\displaystyle \frac{6.023}{9.108}\times 10^{54}$

Show answer
Correct Option: A
Explanation:

Mass of electron $\displaystyle 9.108\times 10^{-31}kg$.
The number of electrons that weigh 1 kg will be $\frac {1}{\displaystyle 9.108\times 10^{-31}}$
The Avagadro number is $\displaystyle 6.023\times 10^{23}$.    
The number of moles of electrons that weigh 1 kg will be
$\frac {1}{\displaystyle 9.108\times 10^{-31} \times \displaystyle 6.023\times 10^{23}}=\displaystyle \frac{1}{9.108\times 6.023}\times 10^{8}$