TOPIC 7 & 8 - NORMALITY, MOLALITY, MOLARITY, MW, EW, MEQ,

MOLARITY

Concentration. The moles of a solute per liters of a solution.

MOLARITY

M

M = MOLES OF SOLUTE / LITERS OF SOLUTION

FORMULA OF MOLARITY

VOLUME (IN LITERS)

MOLARITY RATIO OF MOLES

MOLALITY (m)

Concentration. The moles of a solute per kilograms of a solvent.

MOLALITY

m

m = moles of solute / kg solvent

FORMULA OF MOLALITY

MASS (IN KILOGRAMS)

Molality ratio of moles

0.0854 m salt water

A 25.0 g of NaCl is dissolved in 5,000 mL of water. Find the molality (m) of the resulting solution.

1.81 mol/kg or 1.81 m

A 32.5g of NaF is dissolved in 425g of water. Calculate the molality of the solution.

0.152 M

Calculate the molarity for a solution where you dissolve 50.0 g of calcium nitrate in enough water to make 2.00 L of solution.

0.26 M NaCl

What is the molarity of a solution formed from 6.75 g NaCl dissolved in water to make a solution with a total volume of 452 mL?

0.094 M NaCl

What is the molarity of a solution containing 0.32 moles of NaCl in 3.4 leters?

NORMALITY

a measure of concentration equal to the gram equivalent weight per liter of solution.

NORMALITY

Gram equivalent weight is the measure of the reactive capacity of a molecule.

NORMALITY

also known as the equivalent concentration of a solution.

MOLECULAR WEIGHT

the mass of one mole of a substance. Usually, the units used for this are grams per mole.

H = 1 x 1 = 1
Cl = 1 x 35 = 35
------- 36g/mol (MW)

Compute for the molecular weight of hydrochloric acid (HCl).

EQUIVALENT WEIGHT

the mass of one equivalent, that is the mass of a given substance which will combine with or displace a fixed quantity of another substance.

Eq. Wt = Molecular weight / # of H, OH, total valence of cation

FORMULA OF EQUIVALENT WEIGHT

H = 3 x 1 = 3
P = 1 x 35 = 31
O = 4 x 16 = 64 ------- 98g/mol (MW)

98 / 3 = 32.667 ~32.67 g Ew

Compute for the equivalent weight of phosphoric acid H3PO4.

Na = 1 x 23 = 23
O = 1 x 16 = 16 H = 1 x 1 = 1 ------- 40 g/mol (MW)

40g/mol /1 = 40 g Ew

Solve for the molecular weight: NaOH

Na = 2 x 23 = 46
S = 1 x 32 = 32
O = 4 x 16 = 64 ------- 142 g/mol (MW)

142 / 2 = 71 g Ew

Solve for the molecular weight: Na2 SO4

Ca = 1 x 40 = 40
S = 1 x 32 = 32
O = 4 x 16 = 64 ------- 136 g/mol (MW)

136 / 2 = 68 g Ew

Solve for the molecular weight: CaSO4

Al = 2 x 27 = 54
S = 3 x 32 = 96
O = 12 x 16 = 192 ------- 342 g/mol (MW)

342 / 3 = 114 g Ew

Solve for the molecular weight: Al2 (SO4 )3

H = 2 x 1 = 2
S = 1 x 32 = 32
O = 4 x 16 = 64 ------- 98g/mol (MW)

98 g / 2 = 49 g Ew

Solve for the molecular weight: H2 SO4

MILLIEQUIVALENT (MEQ)

it measures the chemical combining activity of an electrolyte in solution.

MILLIEQUIVALENT (MEQ)

It considers the total number of ions in solution and the valence (charge) of the ions

mEq = mmols x valence or mEq = mg/MW x Valence

FORMULA OF MEQ

mg = mEq x MW / valence

FORMULA OF MG

Millimol (mmol)

the number of millimoles of a substance is calculated by dividing the number of milligrams of substance by the molecular weight of the substance

mmol = mg/MW

FORMULA OF MMOL

41.03 mmol

How many mmols are there in 3.2 grams of calcium fluoride?

7350 mg

How many milligrams of potassium acetate are present in 75 mmols of the substance?

VALENCE

measures its ability to combine with other elements

VALENCE

should be determined based on the number of electrons that would be added, lost, or shared if it reacts with other atoms.

VALENCE

equal to the number of electrons in the outer shell if that number is four or less. Otherwise, it is equal to eight minus the number of electrons in the outer shell.

16.67 mEq

How many mEq of MgSO4 (MW = 120) are represented in 1g of anhydrous magenesium sulfate?

5.95 mEq

Ringer's injection contains 0.86% of sodium chloride, 0.03% of potassium chloride and 0.33% of calcium chloride. How many milliequivalents of calcium chloride are contained in 1 Liter of the injection?