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1. Some basic concept of chemistry — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistry1. Some basic concept of chemistry1 Mark
MCQ
$25.3\ g$ of sodium carbonate, $Na_2CO_3$ is dissolved in enough water to make $250\ mL$ of solution. If sodium carbonate dissociates completely, molar concentration of sodium ion, $Na^+$ and carbonate ions, $CO_3^{2 - }$ are respectively

(Molar mass of $Na_2CO_3 = 106\ g\ mol^{-1} )$

  • A
    $0.955\ M$ and $1.910\ M$
  • ✓
    $1.910\ M$ and $0.955\ M$
  • C
    $1.90\ M$ and $1.910\ M$
  • D
    $0.477\ M$ and $0.477\ M$
✓

Answer

Correct option: B.
$1.910\ M$ and $0.955\ M$
b
Molarity $=\frac{25.3 \times 1000}{106 \times 250}=0.955 M$

$\mathrm{Na}_{2} \mathrm{CO}_{3} \rightarrow 2 \mathrm{Na}^{+}+\mathrm{CO}_{3}^{-2}$

$=2 \times 0.955\;M$

$=1.910 M$

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