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MATTER & CHANGE COURSE
Molarity and Molality
ID: ____________ NAME:
__________________________________________________________
Introduction
The people who work in laboratories use the term concentration
to designate theamount of solute dissolved in a given amount of
solvent. Many of the properties ofthe solutions depend on their
concentrations. The concentration of a solution can be expressed in
a qualitative form orquantitatively.The terms diluted or
concentrated are used to describe a solution in qualitativeform. A
solution with a relatively small concentration of solute says that
it isdiluted; a solution with a high concentration says that it is
concentrated. The chemical concentrations are based on the masses
of solute and arequantitative expressions of the concentration:The
Molarity, (capital letter M) symbolizes the amount of moles of
solute by liter
of solution.The molality, (lower-case latter m) symbolizes the
amount of moles of solute bykilogram of solvent.M = moles of solute
/ liters of solutionm = moles of solute / Kilograms of solventA
solution 1.0 Ms contains 1 mol of solute in each liter of
dissolution. A solution1.0 ms contains 1 mol of solute in each
Kilogram of dissolution.
Problems:
1. Calculate the Molarity of a 250ml aqueous solution of
Sodium
Sulphate (Na2SO4) if 26.5 grams of the sulphate were used.R =
0.74 Ms
Data FormulaSubstitution Result
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2. Calculate the Molarity of an aqueous nitric acid solution
(HNO3) if 48grams of the acid were used to to prepare a liter of
solution.
R = 0.76 Ms
Data FormulaSubstitution Result
3. Calculate the Molarity of an aqueous potassium chloride
dissolution(KCl) if 20 grams of the salt are used to prepare 500
milliliter of
dissolution. R = 0.54 Ms
Data FormulaSubstitution Result
4. How many grams of hydrochloric acid (HCl) are required to
prepare650 milliliters of an aqueous solution at 0.3 Ms? H=1, Cl=
35.5
Data FormulaSubstitution Result
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5. How many grams of potassium bromide (KBr) are required to
preparea 200 milliliter solution at 1.2Ms? K=39, Br=80
Data FormulaSubstitution Result
6. How many grams of sodium bicarbonate (NaHCO3) are required
toprepare a 800 milliliter solution at 2.6 Ms? Na=23, H=1, C=12,
O=16
Data FormulaSubstitution Result
7. How many grams of saccharose (C12H22O11) are needed to
prepare anaqueous dissolution at 0.5ms if 2.5 kg of water were
used? H=1,C=12, O=16
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Data FormulaSubstitution Result
8. How many grams of glycerol (C3H8O3) are needed to prepare
anaqueous solution at 0.8ms if 1500 grams of water were used.
H=1,C=12, O=16
Data FormulaSubstitution Result
9. Calculate the molality of an aqueous solution if 300 grams of
SodiumChloride (NaCl) are mixed with 2.4 kg of water. Na=23,
Cl=35.5
Data FormulaSubstitution Result
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10. Calculate the molality of a hydrobromic acid aqueous
solution if 1.2Liters of water are used to dissolve 150 grams of
the acid. H=1, Br=80
Data Formula
Substitution Result
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