PSC 4012

PSC 4012

Ionic Phenomena:

A study of an environmental problem

PSC 4012: Concentration, Mole & Molarity

Concentration: Amount of solute in a given amount of solution.

Normal Less More


Concentration

c: Concentration

m: Mass of Solute (g)

v: Volume of Solution (L)


Concentration

Change Effect on Concentration

Dilution (Add Solvent) Decreases

Dissolution (Add Solute) Increases

Evaporation (Reduce Solvent) Increases


Calculations

Prepare 4 litres of solution by using 10g of solute. What would be the concentration of this solution?

= 2.5 g/L


Practice:

Organize the following solutions in order of ascending concentration:

S#1: 3g of sugar in 1L of solution

S#2: 5g of sugar in 0.5L of solution



3 g/L

10 g/L

2 g/L

1 g/L

4 - 3 - 1 - 2


Calculations

Sabrina must prepare a solution for a physical science experiment . What mass of salt would she need to prepare 100 mL of solution with a concentration of 20 g/L is needed.

m = (0.1 L) (20 g/L)

m = 2 g


Practice:

Ex. 5.8

p. 5.15


Mole


Mole


Mole


Mole

How many atoms in each situation?

_A dozen of N atoms: 12

_A hundred atoms of O: 100

_A couple of atoms of F: 2

_A mole of Li atoms: 6.02 * 1023


Mole

A mole of anything, is a fixed amount of that item, and it corresponds to Avogadro’s number:

6.02 * 1023

_A mole of houses: 6.02 * 1023 houses

_A mole of cars: 6.02 * 1023 cars

_A mole of molecules: 6.02 * 1023 molecules


Molar mass: The mass of one mole of a given substance

Example: What is the molar mass of water?

Water = H2O (2H and 1O)

Atomic mass of H = 1

Atomic mass of O = 16 g

Molar mass of H2O = (1 + 1 + 16) = 18 g


Practice:

Determine the molar mass of the following substances:

H2

H3PO4

Mg(OH)2

2 g

98 g

58.3 g


Calculations

How many moles are there in 500 g of calcium carbonate?1- calcium carbonate = CaCO3

2- molar mass of CaCO3 = [(1*40)+(1*12)+(3*16)]g

molar mass of CaCO3 = 100 g

3- 100 g = 1 mol

500 g = X (mol)

4- X = 5 mol


Calculations

What is the mass of 0.5 moles of magnesium bromide?1- magnesium bromide = MgBr2

2- molar mass of MgBr2 = [(1*24.3)+(2*80)]g

molar mass of MgBr2 = 184.3 g

3- 184.3 g = 1 mol

X (g) = 0.5 mol

4- X = 92.15 g


Practice:

Ex. 5.17 (a, b, g, h)

p. 5.23 – 5.24


Molar concentration = Molarity

c: Concentration or M (M = mol / L)

n: number of moles of Solute (mol)

v: Volume of Solution (L)


Calculations

What would be the molar concentration of an 800 ml solution containing two moles of sodium chloride?

= 2.5 mol/L = 2.5 M


Practice:

Organize the following solutions in order of ascending molar concentration:

S#1: 3 mol of salt in 1L of solution

S#2: 5 mol of salt in 500mL of solution

S#3: 4 mol of salt in 2L of solution

S#4: 0.1 mol of salt in 100mL of solution

3 mol/L

10 mol/L

2 mol/L

1 mol/L

4 - 3 - 1 - 2


Calculations

Sabrina must prepare a solution for a physical science experiment . What mass of sodium chloride would she need to prepare 750 mL of solution with a molar concentration of 2 M?

n = (2 mol/L) (0.75 L)n = 1.5 mol

Sodium chloride = NaClMolar mass NaCl = [1*23) + (1* 35.5)]g Molar mass NaCl =58.5 g1 mol = 58.5 g1.5 mol = X(g)X = 87.75g NaCl


Practice:

Ex. 5.22

p. 5.29

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PSC 4012