Question

How many (a) molecules (b) hydrogen atoms (c) oxygen atoms are there in 0.5 mole of water?

Answer 1

Answer:

(a) 1 mole of water contains 6.022 × 10²³ molecules

$\therefore \bf 0.5\:\: mol\:\: of\:\: water\:\: contains \:\: \frac{6.022\times 10^{23}}{2} \:\:molecules\\\\=3.011 \times 10^{23}\:\: molecules$

(b) 1 molecules of water contains 2 atoms of hydrogen

1 mol of water contains 2 × 6.022 × 10²³ atoms of hydrogen

$\therefore \bf 0.5\:\: mol\:\: of\:\: water\:\: contains \:\: \frac{2 \times 6.022\times 10^{23}}{2} \:\:atoms\:\: of\:\: hydrogen\\\\=6.022 \times 10^{23}\:\: atoms\:\: of\:\: hydrogen$

(c) 1 molecules of water contains 1 atoms of oxygen

1 mol of water contains 2 × 6.022 × 10²³ atoms of oxygen

$\therefore \bf 0.5\:\: mol\:\: of\:\: water\:\: contains \:\: \frac{6.022\times 10^{23}}{2} \:\:atoms\:\:of\:\:oxygen\\\\=3.011 \times 10^{23}\:\: atoms\:\:of\:\:oxygen$