Question

A coin is made up of Al and weighs $0.75$g. It has a square shape and its diagonal measures 17 mm. it is electrically neutral and contains equal amounts of positive and negative charges. The magnitude of these charges is (Atomic mass of Al = $26.98$g)

• A. $3.47 \times 10^{4}C$
• B. $3.47 \times 10^{2}C$
• C. $1.67 \times 10^{20}C$
• D. $1.67 \times 10^{22}C$

Answer 1

Answer: (A)

$3.47 \times 10^{4}C$

Answer 2

: Mass of the coin $= 0.75g,Z_{Al} = 13$ Atomic mass of aluminum = 26.98 g Avogadro’s number $= 6.02 \times 10^{23}$ Number of Al atoms in the coin,

$N = \frac{6.02 \times 10^{23}}{26.98} \times 0.75 = 1.67 \times 10^{22}$As charge number of Al is 13, each atom of Al contain 13 Protons and 13 electrons. Magnitude of positive and negative charges is one paisa coin

= NZe

$= 1.67 \times 10^{22} \times 13 \times 1.6 \times 10^{- 19}C$

$= 3.47 \times 10^{4}C$