THE MOLE AND THE MASS OF SUBSTANCES

Mass

Amount of substance

2 kg of mangosteen

50 g of flower

3 kg of papaya

What is Molar Mass ???

MOLAR MASS is The mass of one mole of any substance So, the molar mass of 1 mole of an atom is equal to the RELATIVE ATOMIC MASS in gram. Example: Hydrogen: RAM is 1, so it has molar mass of 1 g/mol. Then, the molar mass of 1 mole of molecule is equal to the RELATIVE MOLECULAR MASS in gram. Example: H2O: RMM is 18, so it has molar mass of 18 g/mol.

Dont forget about ionic substance. 1 mole of ionic substance has molar mass that equal to it RELATIVE FORMULA MASS in gram. Example: NaCl: RFM is 58.5, so it molar mass is 58.5 g/mol. The unit for molar mass is g/mol or gmol.

Try these out!!! Find the molar mass of these substances. 1) 2) 3) 4) 5) 6) Carbon,C Calsium sulphate, CaSO4 Benzene, C6H6 Nitric acid, HNO3 Aluminium oxide, Al2O3 Magnesium sulphate, MgSO4

MOLAR MASS RELATION TO AVOGADRO CONSTANT

Molar mass = 1 mol mass 1 mol = 6.02 X 1023

Molar mass = mass of 6.02 X 1023

EXAMPLE

1 mole Aluminum

Relative atomic mass1 mol Aluminum has a mass of 27 g1 mol of Aluminum contain 6.02 X 1023 atoms 6.02 X 1023 Atom of Aluminum has mass of 27g

RELATIONSHIP BETWEEN THE MOLE AND MOLAR MASSMOLE = MASS (g) MOLAR MASS (gmol)

MASS(g) = MOLAR MASS (gmol) x MOLE

X MOLAR MASS

MOLE

MASS(g)

MOLAR MASS

Example 1:What is the mass of a) 0.1 mol of Mg b) 2.408 x 10 atom of Mg (RAM: Mg,24; NA= 6.02 x 10 mol) Solution: 1a) The molar mass of Mg = 24 gmol Mass of Mg = mole x molar mass = o.1 mol x 24 gmol = 2.4 g

1b) The number of moles of Mg atom Mole = number of particles NA = 2.408 x 10 6.02 x 10 = 0.4 mol The mass of 2.408 x 10 Mg atom is = mole x molar mass = 0.4 mol x 24 gmol = 9.6 g

Example 2: How many moles of molecules are there in 16g of sulphur dioxide, SO2? The relative molecular mass of SO2 is = 32 + 16(2) = 64 The molar mass of SO2 = 64 gmol The number of mole of SO2 molecule Mole = mass(g) molar mass (gmol) = 16 g 64 gmol = 0.25 mol

Try these out!!! 1. Calculate the mass in gram of the following a) 0.3 mol Al b) 2 mol of NaNO3 2. How many moles of atoms or molecules are there in a) 5.6g of Fe b) 3.2 g of CH4

THE MOLE AND THE VOLUME OF GAS

WHAT IS MOLAR VOLUME ??????

MOLAR VOLUME

DEFINITION-1 Mole of any gas volume at the S.T.P (Standard Temperature and Pressure) -Its mean, 1 mole any gas at s.t.p equal to 6.02 x 1023 particles Standard temperature is 0oC Standard pressure at 1 atm

Volume gas at the: a) S.T.P

22.4 dm3b)Room temperature

24 dm3

For example:

Volume of 1 mole nitrogen gas at STP is 22.4dm3. Volume of 1 mole oxygen gas at room temperature is 24dm3.

AVOGADRO LAWANY GASES WITH THE SAME VOLUME AT THE SAME PRESSURE AND TEMPERATURE HAVE THE SAME NUMBER OF MOLE MOLECULE

1 MOLE GAS = 6.02 X 1023 particles

RELATIONSHIP BETWEEN GASES VOLUME WITH NUMBER OF MOLES

VOLUMEAT STP

= NUMBER OF MOLE GAS X 22.4 dm3

VOLUME AT ROOM TEMPERATURE

= NUMBER OF MOLE GAS X 24 dm3

NUMBER OF MOLE GAS

=

VOLUME AT S.T.P 22.4 dm3

NUMBER OFMOLE GAS

=

VOLUME AT ROOM TEMPERATURE24 dm3

Example: a) What is the volume of 1.2 mol of ammonia gas, NH3 at S.T.P Solution: The volume of 1.2 mol of NH3 at S.T.P = Mole x Molar volume (S.T.P) = 1.2 mol x 22.4 dm mol = 26.88 dm

b) How many moles of ammonia gas, NH3 are present in 600 cm of the gas measured at room condition? Solution: The number of moles of 600cm NH3 = Volume Molar volume = 0.6 dm 24 dm mol = 0.025 mol.

Try this out!!! 1. Calculate the volume of the following gases: a) 0.3 mol of oxygen gas,O2 measured at room conditions. b) 4 mol of helium gas measured at S.T.P c) 1.5 mol of Hydrogen gas, H2 measured at room condition.

2. Find the number of moles of the following gases: a) 48 dm of chlorine gas,Cl2 at room condition b) 500 cm of carbon dioxide, CO2 at S.T.P c) 960 cm of hydrogen chloride, HCl at room condition.

RELATIONSHIP BETWEEN THE NUMBER OF PARTICLES, NUMBER OF MOLES, MASS AND VOLUME OF GASES

NUMBER OF PARTICLES X NA

X Molar mass

MASS (g)

NA

NUMBER OF MOLES

Molar mass

X Molar volume

Molar volume

VOLUME OF GAS (dm)

Example: How many molecules of carbon dioxide, CO2 are produced when 120 cm of the gas is released during a chemical reaction between an acid and a carbonate at room condition? (molar volume: 24 dm mol at room condition, NA = 6.02 x 10 mol) Solution: Volume of CO2 at room condition = 120 cm Number of molecule = ? Volume of CO2 = 0.12dm The number of mole = volume molar volume = 0.12 dm 24 dm mol = 0.005 mol The number of molecule of CO2 = 0.005 mol x 6.02 x 10 mol = 3.01 x 10 molecule.

Try this out a) A sample of Nitrogen gas, N2 has a volume of 1800 cm at room condition. What is the mass of the sample and how many molecules of Nitrogen gas, N2 are in it? b) Calculate the mass of 1.505 x 10 molecules of Hydrogen gas,H2 at S.T.P