Friday, June 29, 2012

NCERT chemistry 1.5 Calculate the mass of sodium acetate (CH3COONa) required to make 500 mL of 0.375 molar aqueous solution. Molar mass of sodium acetate is 82.0245 g mol–1

Method - 2
mass of sodium acetate = (malrity * molar mass * volume of soultion in ml ) /1000
= .375 * 82.0245 *500/1000 = 15.38 g 

0.375 M aqueous solution of sodium acetate  =  1000 mL of solution containing 0.375 moles of sodium acetate
 
Method - 3 
Number of moles of sodium acetate in 500 mL

                                                                
Molar mass of sodium acetate = 82.0245 g mole–1 (Given)
∴ Required mass of sodium acetate = (82.0245 g mol–1) (0.1875 mole)
Method - 4
You need 500 ml of 0.375 moles/l solution

500ml * 0.375mole/1000ml = 0.1875
moles

1
mole = 82.0245 g

0.1875 moles * 82.0245 g/mole = 15.379 g


take 15.38 g and dissolve to make a 500 ml solution and it will be 0.375 M
Method - 5
first, figure how many moles of sodium acetate / ml of water
you need to produce a 0.375molar sol, do you know your units?

a 1 molar solution = 1mole / litre...

you'll have to forgive chemists for their definitions.

0.375molar solution = 0.375mole / litre

1000mL = 1L

from this : 0.1875moles of sodium acetate multiply by molar

mass and you get your answer.
Method - 6