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3. ATOMS AND MOLECULES
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What is the mass of -
$(a)$ $1$ mole of nitrogen atoms ?
$(b)$ $4$ moles of aluminium atoms (Atomic mass of aluminium $= 27$ ) ?
$(c)$ $10$ moles of sodium sulphite $(Na_2SO_3)$ ?
A
$14\, g$, $108 \,g$ and $256\,g$
B
$140\, g$, $18 \,g$ and $1260\,g$
C
$14\, g$, $90 \,g$ and $126\,g$
D
$14\, g$, $108 \,g$ and $1260\,g$
Solution
$(a)$ Molar mass of $N$ atom $=$ Atomic mass of $N$.
Mass of $1$ mol of $N$ atoms $=14\, g$
$(b)$ Mass of $1$ mole $Al$ atoms $=27 \,g$
Mass of $4$ moles of $Al$ atoms $=27 \times 4=108 \,g$
$(c)$ Mass of $1$ mole of $Na_2 SO_3=(23 \times 2)+32+(16 \times 3)$
$=46+32+48=126\,g$
Mass of $10$ moles of $Na_2 SO_3=126 \times 10=1260\,g$
Standard 9
Science
