According to basic definitions, a solute (e.g. sodium chloride) dissolves in solvent (e.g. water) to make a solution. Concentration indicates how much of a compound (solute) is dissolved in the solution, and can be expressed in multiple ways. Mole fraction refers to the ratio between number of moles of solute and the total number of moles in a solution. As an example, consider calculation of mole fractions in the solution of sodium hydroxide (NaOH) in water (H2O) if NaOH mass percent equals to 10.
Instructions
1. Calculate molecular mass (M) of all compounds (including solvent) that compose the solution. Generally, for a compound with chemical formula AnBm:
Molecular mass (M) = n x M(A) + m x M(B), where M(A) or M(B) are atomic weights of the corresponding elements, which can be taken from the periodic table of the chemical elements.
In our example
M(NaOH)=M(Na)+M(O)+M(H)=23+16+1=40 g/mole.
M(H2O)=2xM(H)+M(O)=2 x 1+16=18 g/mole.
2. Calculate masses of solute and solvent in the solution. Mass percent (solute)=100percent x[mass(solute)/(mass(solution)). Abbreviate mass(solution) as "m" for simplicity and obtain: mass(solute)= m x [mass percent (solute)/100percent], and mass(solvent)= m-mass(solute).
In our example:
mass(NaOH)=m x [10 percent/100 percent]= 0.10m
mass(H2O)=m-0.1m=0.9m.
3. Calculate amount of solute and solvent in Moles: amount =mass/molecular mass (mole)
In our example:
amount (NaOH)=0.1m/40 (mole)=0.0025m (mole)
amount(H2O)=0.90m/18 (mole)=0.05m (mole)
4. Calculate mole fractions. The mole fraction of the component X of the solution is
Mole fraction (X)=amount(X)/[Total amount (sum) of all components]
In our example, NaOH and H2O are only two components i.e.
Mole fraction(NaOH)=0.0025m/(0.0025m+0.05m)= 0.0025/0.0525=0.048
Mole fraction(H2O)=0.05m/(0.0025m+0.05m)= 0.05/0.0525=0.952
Related posts
Calculate Mg per MlCalculating milligrams (mg) per milliliter (ml) is a common task when you work with chemicals of all kinds. It is especially important when determining drug dosages, since the a...
Calculate Bond AnglesBond angles refer to the angles created in the formation of molecular compounds. When molecular compounds are created, a variety of bond angles are possible based on the orien...
Removing facial hair can be done using hydrogen peroxide.Peroxide is a common product used for lightening mustaches. This is commonly done when a woman has a small mustache on her face. This can b...
Life insurance comes at different costs depending on the buyer.Life insurance is sold under a few different types of policies. Term life and mortgage insurance are temporary policies that remain i...
Measurements Used to Calculate PrejudiceWhen the woman in an adjoining cubicle announced, "I Jewed him down and got a great price," one of her neighbor's hot buttons was triggered, and s...
