question_answer

25.3 g of sodium carbonate, \[N{{a}_{2}}C{{O}_{3}}\] is dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, molar concentration of sodium ion, \[N{{a}^{+}}\] and carbonate ion, \[CO_{3}^{2-}\] are respectively     (Molar     mass     of\[N{{a}_{2}}C{{O}_{3}}=106\,g\,\,mo{{l}^{-1}}\])           [AIPMT (S) 2010]

A)  0.955 M and 1.910 M

B)  1.910 M and 0.955 M

C)  1.90 M and 1.910 M

D)  0.477 M and 0.477 M

Correct Answer: B

Solution :

Molarity

in aqueous solution remains dissociated as

Since, the molarity of is 0.955 M, the molarity of is also 0.955 M and that of Na+ is 2 x 0.955=1.910 M