Calculate the molality of the salt solution Chemists often use molarity M. in mo

Question

Calculate the molality of the salt solution Chemists often use molarity M. in moles/liter to measure the concentration of solutions Molarity is a common unit of concentration because the volume of a liquid is very easy to measure However. the drawback of using molarity is that volume is a temperature-dependent Quantity As temperature changes, density changes, which affects volume, Volume marking for most laboratory glassware are calibrated for room temperature, about 20 degree C Fortunately. there are several other ways of expressing concentrator that do not involve volume and are therefore temperature independent. Calculate the mole fraction of salt in this solution Calculate the concentration of the salt solution in percent by mass.

Explanation / Answer

given-A mass of 0.630g of NaCl is dissolved in 525 g of water

A)molality= moles of salt/kg of solvent

moles of NaCl=mass/molar mass=0.630g/58.44 g/mol=0.0108 moles

molality=0.0108 moles/0.525kg=0.0206m

B)mole fraction=moles of salt/moles of salt +moles of water

moles of water=525g/18 g/mol=29.17 moles

mole fraction=0.0206/0.0206+29.17=0.0206/29.187=7.06*10^-4

C)concentration in % by mass=(mass of salt /total mass of solution )*100=(0.630/0.630+525)*100=0.630/525.630 *100=0.12%

D)concentration in ppm or mg/kg(w/w)=0.630*1000 mg/525*10^-3 kg=0.0012*10^-6=0.0012 ppm(w/w)

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