Question

calculate the mass of nacl required to produce 100ml of semimolar solution​

Answer 1

1/2* molecular mass of Nacl =1/2*58.5=29.25 g

explanation: since given is semimolar soln = molarity =1/2 now molarity is nothing but moles of solute in 1000 ml sol.but here it is asked in 100 ml soln ,it does'nt matter take it out in 1000 ml .

so we know that mass = moles * molecular mass =1/2*58.5=29.25

Answer 2

Answer:

73 g

Explanation:

The molecular weight of NaCl is 58.44 g/mol

So, one mole of NaCl weighs 58.44 g.

A 2.5 M solution is 2.5 moles per liter (Molarity is just the number of moles per liter).

Therefore, 0.5 L would contain 1.25 mol. Hence, you would need 1.25 × 58.44 g = 73 g.

As equations:

M = moles vol

M = Molarity

vol = volume (in liters)

moles = grams M W

g = weight of compound

M W = molecular weight

So,

M = moles vol

Substitute for moles

M = g / M W vol

We need g , so rearrange

M × vol = g M W

g = M × vol × M W

Put in the numbers:

g = 2.5 mol/L × 0.5 L × 58.44 g/mol

g = 73 g

Personally, I prefer the first approach!

You can find out more about moles and molarity here .