Chem class(1mac)

4S6Welcome To the Chemistry World~

Cl-

Zn2+

Cl-

1 Zn2+ ion 2 Cl- ions1 ZnCl2 =

3.4 THE MOLE AND THE VOLUME

- the molar volume of a gas is the volume occupied by one mole of the gas or particles of gas

- one mole of any gas always has the same volume under the same temperature and pressure.

- the molar volume of any gas at STP is ________________.

-Standard Temperature and Pressure (STP) is the conditions where temperature is ______ and pressure is ________.

Example: a. 1 mole of oxygen gas = _____________ b. 1 mol of carbon dioxide gas= _____________ c. 1 mol of ammonia gas = _______________

22.4 dm3mol-1

0°C

1 atm

22.4 dm3mol-1

22.4 dm3mol-1

22.4 dm3mol-1

- the molar volume of any gas at room temperature is ________________.

-At room temperature is the conditions where temperature is ______ and pressure is ________.

Example: a. 1 mole of oxygen gas = _____________ b. 1 mol of carbon dioxide gas= _____________ c. 1 mol of ammonia gas = _______________

24 dm3mol-1

24 dm3mol-1

24 dm3mol-1

24 dm3mol-1

25°C 1 atm

(More Van More Vibrate)

Molar volume

Volume

Number of Moles

RTP =24 dm3mol-1

STP=22.4 dm3mol-1

EXAMPLE 1:

What is the volume of 2.5mol helium gas at s.t.p?

Volume of gas = No. of moles x molar volume= 2.5 mol x 22.4dm3mol-1

= 56 dm3

22.4 dm3mol-1

EXAMPLE 2:

What is the number of moles in 240 cm3 oxygen gas at r.t.p?

number of moles = volume of the gas

Molar Volume= 0.24 dm3 24 dm3 mol-1

= 0.01 mol 240 cm3 = 2401000

= 0.24dm3

24 dm3mol-1

EXAMPLE 3:

Calculate the volume of the gases at room temperature and pressure that contains:

a. 12 x 1022 C3H8 molecules

b. 2.4 x 1023 N2 molecules

(1 mole of gas occupies 24 dm3at room temperature; NA= 6 x 1023 )

CALCULATE THE VOLUME OF THE GASES AT ROOM TEMPERATURE AND PRESSURE THAT CONTAINS:A. 12 X 1022 C3H8 MOLECULES

Number of mole = 12 x 1022

6 x 1023

= 0.2 mol

Volume = 0.2 x 24dm3 = 4.8dm3

24 dm3mol-1

CALCULATE THE VOLUME OF THE GASES AT ROOM TEMPERATURE AND PRESSURE THAT CONTAINS:B. 2.4 X 1023 N2 MOLECULES

Number of mole = 2.4 x 1023

6 x 1023

= 0.4 mol

Volume= 0.4 x 24dm3 = 9.6 dm3

ANSWER

a) Number of mole = 12 x 1022

6 x 1023

= 0.2 mol

1 mole of gas occupies 24dm3 at room temperature0.2 mole gas occupies 0.2 x 24dm3 = 4.8dm3

b) Number of mole = 2.4 x 1023

6 x 1023

= 0.4 mol

1 mole of gas occupies 24dm3 at room temperature0.4 mole gas occupies 0.4 x 24dm3 = 9.6 dm3

EXAMPLE 4:

a. What is the volume of 4g of oxygen gas in cm3 at STP?

b. A sample of hydrogen gas contains molecules. Find the mass of the hydrogen gas.

c. How many molecules are there in 7840 cm3 of ammonia gas in STP?

WHAT IS THE VOLUME OF 4G OF OXYGEN GAS IN CM3 AT STP?

Number of mole = 4g

32gmol-1

= 0.125 mol

Volume = 0.125mol x 22.4 dm3 mol-1 = 2.8dm3 = 2800cm3

A SAMPLE OF HYDROGEN GAS CONTAINS 1.806 X 1023

MOLECULES. FIND THE MASS OF THE HYDROGEN GAS.

Number of mole = 1.806 x 1023

6.02 x 1023

= 0.3 mol

mass of the hygrogen gas = 0.3 mol x 2gmol-1 = 0.6g

C. HOW MANY MOLECULES ARE THERE IN 7840 CM3 OF AMMONIA GAS IN STP?

7840cm3 = 7840÷ 1000= 7.84dm3

Number of mole = 7.84dm3

22.4dm3mol-1

= 0.35 mol

Number of molecules = 0.35 mol x 6.02 x 1023 = 2.107 x 1023 molecules

a. Number of mole = 4g 32gmol-1

= 0.125 mol

0.125 mol of oxygen gas = o.125mol x 22.4 dm3mol-1 = 2.8dm3 = 2800cm3

b) Number of mole = 1.806 x 1023

6.02 x 1023

= 0.3 mol

0.3 mol of hydrogen gas = 0.3 mol x 2gmol-1 = 0.6gc) 7840cm3 = 7840÷ 1000= 7.84dm3 Number of mole = 7.84dm3 22.4dm3mol-1

= 0.35 mol

0.35 mol of ammonia gas = 0.35 mol x 6.02 x 1023 = 2.107 x 1023 molecules

CHEMISTRY FORMULAE

A CHEMICAL FORMULA is a representation of a _______________________ using symbols of the elements and subscript numbers to show the numbers of each type of atoms that are present in the substance.

Chemical substance

CHEMICAL FORMULA

sodium chloride

NaNaCl

The overall charge

must be 0

-+

Cl

CALSIUM FLOURIDE

Ca

The overall charge

must be 0

-2+

F

CaF2

MAGNESIUM CHLORIDE

Mg

The overall charge

must be 0

-2+

Cl

MgCl2

MAGNESIUM SULPHATE

Mg

The overall charge

must be 0

2-2+

SO4

MgSO4

Put in simplest ratio

ALUMINIUM OXIDE

Al

The overall charge

must be 0

2-3+

O

Al2O3

AMMONIUM SULFATE

NH4

The overall charge

must be 0

2-+

SO4

(NH4 )2 SO4

LEAD (II) HYDROXIDE

Pb

The overall charge

must be 0

-2+

OH

Pb ( OH )2

NAMING

Naming of cations of fixed oxidation state Naming of cations of variable oxidation state

Naming of anions – ide ate- (Fat) – more oxygen Ite – (Fit )– less oxygen

CATIONS OF FIXED OXIDATION STATE Sodium ion (Na+) Eg: Sodium chloride (NaCl)

Magnesium ion (Mg2+) Eg: Magnesium oxide (MgO)

Calcium ion(Ca2+) Eg: Calcium carbonate (CaCO3)

Aluminium ion (Al3+) Eg: Aluminium oxide (Al2O3)

CATIONS OF VARIABLE OXIDATION STATE Iron(ll) ion (Fe2+)

Eg: Iron(II) chloride (FeCl2)

Iron(lll) ion (Fe3+)

Eg: Iron(III) chloride (FeCl3)

Copper (l) ion (Cu+)

Eg: Copper(I) oxide (Cu2O)

Copper (ll) ion(Cu2+)

Eg: Copper(II) oxide (CuO)

Lead(ll) ion(Pb2+)

Eg: Lead(II) oxide (PbO)

Lead(lV) ion (Pb4+)

Eg: Lead(IV) oxide (PbO2)

PREFIXES

Mono 1 Di 2 Tri 3 Tetra 4 Penta 5

NAMING OF CHEMICAL COMPOUND

Fe2O3

Fe3+

Iron(III) oxide

O2-

NAMING OF CHEMICAL COMPOUND

PbO2

Pb4+ O2-

Lead (IV) oxide

NAMING OF CHEMICAL COMPOUND

ZnO NaNO3 SO3 Fe2O3 CCl4 N2O4 CaCl2 PbI2 PbO2 K2CO3 PCl5

Zinc oxideSodium nitrateSulphur trioxide

Iron(III) oxideCarbon tetrachlorideDinitro tetraoxideCalcium chlorideLead(ll) Iodide

Potassium carbonatePhosphorus pentachloride

Lead (IV) oxide

PASS UP ON MONDAY(4/3/2013)

Spotlight access 3.4

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