(a) No of H₂O particles:

No of moles = 2

1 mole = 6.022 x 10²³

Thus, 2 moles of H₂O = 2 X 6.022 x 10²³ = 12.044 x 10²³ particles

(b) (i) No of moles of CO₂:

we know,

1 mole = 6.022 × 10²³

The number of moles

(ii) Thus, The number of moles =

Given mass = Number of moles x Molar mass

= 0.5 x 44

= 22g

(c) (i) The number of moles =

Molar mass of Na = 23g/mole

Given mass = 115g

Thus, the number of moles =

(ii) 1 mole = 6.022 x 10²³

Since, 5 moles = 5 x 6.022 X 10²³ = 30.11 X 10²³

(d) (i) No of moles of MgCl₂ = 0.5

The number of moles =

Molar mass of MgCl₂ = 95g/mole

Thus, mass of MgCl₂ = 0.5 X 95 = 47.5g

(ii) Number of particles: 1 mole = 6.022 x 10²³

0.5 mole = 0.5 x 6.022 x 10²³

Number of particles= 3.011 x 10²³