# chemistry

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how many grams of NAOH are needed to make a 2.00 molal solution?

I got stuck here

2.00 molal=2.00 mole/kg
molecular weight of NAOH= 40g/mol

(2.00 g/molecular weight x kg) x 40 g/mol= stuck

thanks jim

• chemistry - ,

You cant answer the question without knowing the amount of the 2m solution you need.

molality=molessolute/kgsolvent
molessolute=molalitiy*kgsovent
masssolute=molmassSolute*molality*kgsolvent
masssolute=40*2*kgsolvent

• chemistry - ,

Doesn't it depend upon the amount of water you intend to use or the amount of solution one needs? (It does.)
So molal = # moles/kg solvent.
If you want 1 kg solvent, one needs 2.00 moles and that is 40.0 g. So 40.0 g NaOH/1.00 kg water makes a 2.00 m solution.

• chemistry - ,

damn i never thought of kg of solution. your so smart.

2.00mol x 40 g/m= 80grams dissolved in water. so 80 grams of solute and 1000 water.

Chemistry doesnt make sense too me sometimes. Im use to thinking water =ml. But kg can be a solution too if you weigh it on an analytical balance.

Can help me learn to volumetric pipette. I can\t seem to control the water with my finger. It always goes over line. Very fustrating to start over and over.