Question

Weight of KOH should be dissolved in 100 ml of water to prepare 0.2 M solution is (Assume no change in volume) [ Also provide explanation]
(A) 1.12 gm
(B) 11.2 gm
(C) 5.6 gm
(D) 0.56 gm​

Answer 1

Answer:

firstly find the no. of moles to solve further..

we know

molarity = no. of moles/ volume of solution in litre

if volume is in ml then convert it in litre..

this implies,

0.2 = number of moles x 1000/100

0.2 = number of moles x 10

so the number of moles = 0.02u

and number of moles = given mass / molecular mass

here the moleculer mass of KOH is 39+ 16+1 = 56u

put the molecular mass in above formula..

0.02 = given mass / 56

given mass = 1.12gm

so the correct answer is option A i.e. 1.12 gm

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Answer 2

Answer:

firstly find the no. of moles to solve further..

we know

molarity = no. of moles/ volume of solution in litre

if volume is in ml then convert it in litre..

this implies,

0.2 = number of moles x 1000/100

0.2 = number of moles x 10

so the number of moles = 0.02u

and number of moles = given mass / molecular mass

here the moleculer mass of KOH is 39+ 16+1 = 56u

put the molecular mass in above formula..

0.02 = given mass / 56

given mass = 1.12gm

so the correct answer is option A i.e. 1.12 gm

Explanation: