Avogadro’s ConstantAvogadro’s Constant

What is it and what information What is it and what information does it give us?does it give us?

Why are moles Why are moles important?important?

As scientists we add elements As scientists we add elements together to make new substancestogether to make new substances

We like to work out the ratios before We like to work out the ratios before we do this so that there is no wastewe do this so that there is no waste

Example: a food recipe, you don’t’ Example: a food recipe, you don’t’ want too many eggs as it will spoil the want too many eggs as it will spoil the cakecake

What Avogadro did for usWhat Avogadro did for us

He worked out an exact figure for the He worked out an exact figure for the quantity of carbon present in 12 gramsquantity of carbon present in 12 grams

This is a measure of the number of This is a measure of the number of atoms presentatoms present

This allows us to compare atoms in terms This allows us to compare atoms in terms of ratiosof ratios

6.02 x 1023

Avogadro’s numberAvogadro’s number

What does this number represent? What does this number represent? Which element did it refer to?Which element did it refer to? How many particles are present in 2 moles of How many particles are present in 2 moles of

Na?Na? How many particles are present in 0.5 moles of How many particles are present in 0.5 moles of

Fe?Fe? How many moles are there in 4.167 x10How many moles are there in 4.167 x101414

of of particles Pb?particles Pb?

6.02 x 1023

Molecular formulaMolecular formula

What is meant by molecular formula?What is meant by molecular formula? How can it be calculated?How can it be calculated? What is the molecular formula for:What is the molecular formula for:

waterwater magnesium chloridemagnesium chloride potassium oxidepotassium oxide silicon iodidesilicon iodide

Empirical formulaEmpirical formula

This is the simplest ratioThis is the simplest ratio is the molecular formula for is the molecular formula for

ethene, but its empirical formula is Cethene, but its empirical formula is C11 : H : H22

What is the empirical formula for:What is the empirical formula for:

C2H4

C6H12O6 C4H8Cl2 CH3COOH

Calculating the empirical formula from the percentage massesCalculating the empirical formula from the percentage massesIf a compound gives the following results when analysed, 87.7% If a compound gives the following results when analysed, 87.7% C and 14.3% HC and 14.3% H

What is the empirical and molecular What is the empirical and molecular formula?formula?

87.7/12 = 7.1 carbon87.7/12 = 7.1 carbon 14.3/1 = 14.3 hydrogen14.3/1 = 14.3 hydrogen What is the lowest ratio between these What is the lowest ratio between these

numbers?numbers?

Molecular formula:Molecular formula:If a mass of a hydrocarbon equals 42, If a mass of a hydrocarbon equals 42,

what is the molecular formula?what is the molecular formula?

Work out the following Work out the following the empirical formula equals C1:H2the empirical formula equals C1:H2

Concentration and Concentration and MolarityMolarity

What is a solute, solvent and a solution?What is a solute, solvent and a solution?

What do we mean by the concentration of something? What do we mean by the concentration of something? Write a sentence to express when something is more Write a sentence to express when something is more concentrated. Use the following words, volume, solute, concentrated. Use the following words, volume, solute, solvent solvent

Can you remember the equation that calculates the Can you remember the equation that calculates the concentration of a liquid?concentration of a liquid?

Moles = Conc x Volume

How do we measure liquid How do we measure liquid concentrations?concentrations?

When 1 mole of solute is dissolved in 1 When 1 mole of solute is dissolved in 1 decimetre of solution, its concentration is decimetre of solution, its concentration is said to be 1 mol dm-3said to be 1 mol dm-3

This is called 1 M for shortThis is called 1 M for short We measure concentration in molarityWe measure concentration in molarity

1 dm3 = 1000cm3 = 1 litre

Work out how much compound would be Work out how much compound would be needed to make a 1 molar solution for the needed to make a 1 molar solution for the followingfollowing

1.KHCO3

2.NaCl

3.Li2O

ExampleHow many moles are there dissolved in

200 cm3

of 1 M solution of NaHCO3

200/1000 x 1 = 0.2 moles

Work out the molarity of questions 4-6Work out the molarity of questions 4-6

4.KHCO3 1 mole is dissolved in 2 litres of water 1/2

5.NaCl 2 moles is dissolved in 500cm3 of water 2/0.5

6.Li2O 0.5 moles dissolved in 1.5 dm3 of water 0.5/1.5

How can we work out the amount How can we work out the amount of solid dissolved in a liquid?of solid dissolved in a liquid?

Work out the amount of solid dissolved in each solutionExample:

Work out the number of moles the times by the mass200/1000 x 1M = 0.2 moles of LiOH

0.2 x 24 (Li = 7 and OH = 17, 7 + 17 = 24)

1.2 grams of LiOH

Calculate the following:Calculate the following:

1.KHCO3 1 mole is dissolved in 2 litres of water

2.NaCl 2 moles is dissolved in 500cm3 of water

3.Li2O 0.5 moles dissolved in 1.5 litres of water

The purpose of a titrationThe purpose of a titration

To find the concentration To find the concentration of a unknown solutionof a unknown solution

Comparing the unknown Comparing the unknown to a known solution to a known solution

Helps us calculate the Helps us calculate the amount of acid or alkali amount of acid or alkali present present

When would this be used When would this be used in the real world?in the real world?

You have created a known molarity You have created a known molarity for the alkali sodium hydroxide:for the alkali sodium hydroxide:

Work out the mass of NaOHWork out the mass of NaOH Na = 23 O = 16 H = 1 add together = 40Na = 23 O = 16 H = 1 add together = 40 Molarity = 250/1000 = 0.25 0.25/0.25 = 1.0 molar or Molarity = 250/1000 = 0.25 0.25/0.25 = 1.0 molar or

1M1M Now you can work out the molarity of the unknown Now you can work out the molarity of the unknown

substance:substance:

Measure a known volume of acid and add indicatorMeasure a known volume of acid and add indicator Neutralise the acidNeutralise the acid What equation would you use?What equation would you use?

Results: Results: Vol acid = 25cm cubedVol acid = 25cm cubedVol alkali needed to neutralise = 26.5 cm cubed Vol alkali needed to neutralise = 26.5 cm cubed Conc of alkali = 0.95 molarConc of alkali = 0.95 molar

Molarity of known substance x Volume =

Molarity of unknown substance x volume

Substitute in what you know0.95 x 26.5 = ? x 25

=1.007

Equations:Equations:

Write a balanced equation for the Write a balanced equation for the reaction between hydrochloric acid and reaction between hydrochloric acid and sodium hydroxidesodium hydroxide

Follow this with an ionic equationFollow this with an ionic equation

NaOH (aq) + HCl (aq) = NaCl (aq) + H2O (l)

For the following examples balance the equation For the following examples balance the equation putting state symbolsputting state symbols

1.NH3 + O2 = NO2 + H2O

2.C2H5OH + O2 = CO2 + H2O

3.Al + NaOH= Na3AlO3 + H2

4.CO2 + H2O = C6H12O6 + O2

5.C3H8 + O2 = CO2 + H2O

6.4Al + 12H2SO4 = 2Al2(SO4)3 + 6SO2 + 12H2O

You have just done an experiment and made You have just done an experiment and made Ammonium Sulphate. You started out with 8.6g of Ammonium Sulphate. You started out with 8.6g of Ammonium hydroxide.Ammonium hydroxide.

What would you react this with to make a sulphate? What is the What would you react this with to make a sulphate? What is the new class of substance you have made? What is this type of new class of substance you have made? What is this type of reaction called?reaction called?

What is the maximum amount you could make?What is the maximum amount you could make?Hint: Moles = mass/ molecular massHint: Moles = mass/ molecular mass

You also need to work out the products and ratios in the reaction first.You also need to work out the products and ratios in the reaction first.

Now calculate the actual yield when:Now calculate the actual yield when: The experimental value of the substance is 10.64g How did The experimental value of the substance is 10.64g How did

I work this out?I work this out?Hint: you need to compare it to your 100% theoreticalHint: you need to compare it to your 100% theoretical

The experiment was done again, the The experiment was done again, the yield went up to 83%, what was the yield went up to 83%, what was the amount made?amount made?

What could have been done What could have been done differently? Why will you always not differently? Why will you always not get less than 100% yield no matter get less than 100% yield no matter how careful you are?how careful you are?

Look at what changes in the ions, first you will Look at what changes in the ions, first you will need to write out the ions as they existneed to write out the ions as they exist

Cancel out the ones that don’t change.Cancel out the ones that don’t change. Then construct an equation will the essential ions Then construct an equation will the essential ions

present only.present only. Try this one now using the same rulesTry this one now using the same rules

Example: 2NH4OH + H2SO4 = (NH4)2 SO4 + 2H2O

CaCO3 + HCl = CaCl2 + CO2 + H2O

Mg + 2HCl = MgCl2 + H2

Working out reacting gas amountsWorking out reacting gas amounts

What equation do we What equation do we use to calculate gas use to calculate gas quantities?quantities?

If 1.5 dm cubed of Hydrogen If 1.5 dm cubed of Hydrogen was produced from was produced from hydrochloric acid when hydrochloric acid when magnesium dissolved, how magnesium dissolved, how much magnesium was there much magnesium was there to start with?to start with?

Hint- start with the equationHint- start with the equation

Equal volumes of all gases at the same Equal volumes of all gases at the same pressure and temperature contain the same pressure and temperature contain the same number of particles (same number of moles)number of particles (same number of moles)

Work out the moles Work out the moles of potassium nitrateof potassium nitrate

Work out the volume Work out the volume of oxygen producedof oxygen produced

1.Calculate how many dm3 of hydrogen gas are produced when 19.5g of zinc metal dissolved in excess hydrochloric acid at 30oC and 100 KPa.

2.C8H18 + O2 = CO2 + H2O

Balance this

What volume of oxygen reacts with 10 dm3 of petrol?

How many moles of petrol are there?

How many moles of oxygen are required?

What is the mass of CO2 produced?

Calculate the volume of gas produced when 150g of calcium carbonate decomposes to form calcium oxide and carbon dioxide in dm3 at 100 KPa and 25oC

Hard water from a town’s water supply was measured and found to be 0.4g in 1m3 (The calcium carbonate was weighed after the water was boiled off).

Calculate: Calculate: Work out the number of moles present Work out the number of moles present Work out the molarity Work out the molarity The calcium carbonate was reacted with sulphuric acid, write a balanced The calcium carbonate was reacted with sulphuric acid, write a balanced

symbol equation for this putting in the number of moles of each and the symbol equation for this putting in the number of moles of each and the massesmasses

H2SO4 + CaCO3 = CaSO4 + CO2 + H2O

Write a ionic equation for this reactionWrite a ionic equation for this reaction

An organic compound is shown to have An organic compound is shown to have 40% carbon, 6.7% hydrogen and 53.3% 40% carbon, 6.7% hydrogen and 53.3% oxygenoxygen

Deduce the empirical formulaDeduce the empirical formula It is shown to have a mass of 180, It is shown to have a mass of 180,

deduce the molecular formuladeduce the molecular formula

A company that makes vinegar has to print the A company that makes vinegar has to print the percentage amount of organic acid on their bottles, a percentage amount of organic acid on their bottles, a reaction between sodium hydroxide was undertaken. reaction between sodium hydroxide was undertaken. 25 cm3 reacted with 29cm3 of 0.1 M of the alkali.25 cm3 reacted with 29cm3 of 0.1 M of the alkali.

Work out the concentrationWork out the concentration The amount of carbon was found to be 48.7%, The amount of carbon was found to be 48.7%,

hydrogen was 8.1% and oxygen was 43.2, work out the hydrogen was 8.1% and oxygen was 43.2, work out the empirical formulaempirical formula

The mass of the acid is 74, work out the formulaThe mass of the acid is 74, work out the formula Write an equation for the neutralization reaction, what Write an equation for the neutralization reaction, what

is the name of this acid?is the name of this acid?

Greenhouse gasesGreenhouse gases

What is the relationship, if What is the relationship, if any?any?

What is the amount of gases What is the amount of gases measured in?measured in?

Explain what the greenhouse Explain what the greenhouse effect iseffect is

What other proof is there What other proof is there available that COavailable that CO22 has an has an effect on the atmospheric effect on the atmospheric temperature?temperature?

Answer: Venus atmosphere is Answer: Venus atmosphere is 96% CO96% CO2 2 and the temp is and the temp is 450450ooCC

Which gases Which gases cause the most cause the most warming of the warming of the planet?planet?

Which are the Which are the most abundant most abundant greenhouse greenhouse gases?gases?

On earth, the most abundant greenhouse gases are, in On earth, the most abundant greenhouse gases are, in order of relative abundance:order of relative abundance:

water water vaporvapor carbon dioxidecarbon dioxide methanemethane nitrous oxidenitrous oxide ozoneozone CFCsCFCs The most powerful greenhouse gases areThe most powerful greenhouse gases are water water vaporvapor, which causes about 36–70% of the , which causes about 36–70% of the

greenhouse effect on Earth. (Note clouds typically greenhouse effect on Earth. (Note clouds typically affect climateaffect climate differently from other forms of differently from other forms of atmospheric water.) atmospheric water.)

carbon dioxidecarbon dioxide, which causes 9–26% , which causes 9–26% methanemethane, which causes 4–9% , which causes 4–9% ozoneozone, which causes 3–7% , which causes 3–7%

Work out the Work out the percentages present in percentages present in the double saltthe double salt

Ammonium iron (II) Sulphate can be Ammonium iron (II) Sulphate can be made from iron, ammonia and sulphuric made from iron, ammonia and sulphuric acid.acid.

Write the individual equations for eachWrite the individual equations for each If 25cmIf 25cm33 of 1.0 M H of 1.0 M H22SOSO44 is used work out the mass of is used work out the mass of

FeSOFeSO44 made from 1.12g of Fe made from 1.12g of Fe The remainder of the acid reacts with the ammonia, The remainder of the acid reacts with the ammonia,

work out the mass of ammonium sulphate made.work out the mass of ammonium sulphate made. The total mass of the dried combined salts is 2.8g, The total mass of the dried combined salts is 2.8g,

workout the 100% theoretical mass then calculate what workout the 100% theoretical mass then calculate what the yield is? the yield is?

Fe + HFe + H22SOSO44 = FeSO = FeSO44 + H + H22 Mass 1.12gMass 1.12g 1.96 3.04 ? 1.96 3.04 ? Moles 0.2 0.025 0.2 ?Moles 0.2 0.025 0.2 ?

2NH2NH33 + H + H22SOSO44 = (NH = (NH44))22SOSO44 Mass ?Mass ? ? ? ? ? Moles ? 0.005 ?Moles ? 0.005 ?

Work out the missing masses and molesWork out the missing masses and moles