Tag: discovery of subatomic particles

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

Select the correct statement?

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

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

  2. 16
  3. $12.04 \times 10^{23}$
  4. $6.023 \times 10^{24}$
Reveal answer Fill a bubble to check yourself
A Correct answer
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
Multiple choice chemistry atom fundamental particles of an atom the structure of atoms discovery of subatomic particles

The molar mass of an electron is:

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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

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

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

  1. $6.023\times 10^{22}$
  2. $10.8576\times 10^{23}$
  3. $10.8576\times 10^{22}$
  4. $6.023\times 10^{23}$
Reveal answer Fill a bubble to check yourself
D Correct answer
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 $=6.023\times 10^{22}\times10=6.023\times 10^{23}$

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

How many moles of electron weighs one kilogram?

  1. $6.023\times 10^{23}$
  2. $\dfrac {1}{9.108}\times 10^{31}$
  3. $\dfrac {6.023}{9.108}\times 10^{54}$
  4. $\dfrac {1}{9.108\times 6.023}\times 10^8$
Reveal answer Fill a bubble to check yourself
D Correct answer
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 $D$

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

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 $)

  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. $\displaystyle \frac{6.023}{9.108}\times 10^{54}$
Reveal answer Fill a bubble to check yourself
A Correct answer
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
$\frac {1}{\displaystyle 9.108\times 10^{-31} \times \displaystyle 6.023\times 10^{23}}=\displaystyle \frac{1}{9.108\times 6.023}\times 10^{8}$