Question

49. If molarity of 100 ml sodium hydroxide solution is
0.5, then the mass of sodium hydroxide present in
the solution is (Atomic weight of Na = 23)
(1) 5 g
(2) 2g
(3) 4 g
(4) 2.59​

Answer 1

Answer: the answer is 2g

Explanation: mil.mass of NaOH=40g Molarity=.5 Volume=100ml or 100/1000 L

FROM the formula of molarity i.e.,

MOLARITY= MOLES/VOLUME OF SOLUTION IN (LITERS)

Thereby MOLES=MOLARITY× VOL (L)

MOL= 0.5×100/1000

MOLES = 0.05

BY MOLES= mass/ molar mass

MASS = MOLES × MOL.MASS

MASS=.05×40=2g