Ncert Exercises & Solutions

Mark the species among the following that contains the highest number of atoms:

1. 4 g He

2. 46 g Na

3. 0.40 g Ca

4. 12 g He

Hint: 1 mol of an element is equal to it atomic mass

Step 1:

For comparing number of atoms, first we calculate the moles as all are monoatomic and hence,

moles \times N_{A} = number

of

atoms .

Step 2:

Calculate the moles of given elements as follows:

Moles

of

4

g

He = \frac{4}{4} = 1

mol

46

g

of

Na = \frac{46}{23} = 2

mol

0.40

g

Ca = \frac{0.40}{40} = 0.1

mol

12

g

He = \frac{12}{4} = 3

mol

Hence, 12 g He contains greater number of atoms as it possesses maximum number of moles.