# C5 - How Much?

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## Moles and Emprical Formulae & Electrolysis - Quest

Moles and empirical formulae

• What is the molar mass of this acid: Ch3C(CH)2COOH ?
• How much carbon dioxide is made when 440g propane, C3H8 is burned?
• What is the empirical formula for hexane, C6H14?
• 110g of sulfuric acid contains 2.04%H, 32.65% S and 65.31% O. Work out the empirical formula of sulfuric acid.

Electrolysis

• Which type of ions move towards the cathode during electrolysis?
• Write down two half equations that represent electrolysis of Pbl2
• Write down two quantities that change the amount produced at an electrode.
• How much charge is transferred by a current or 0.2A for 3 hours?
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## Moles and Emprical Formulae & Electrolysis - Answe

Moles and Empirical Formulae

• 90
• 1320g
• C3 H7
• H2 SO4

Electrolysis

• Negative ions - cations.
• Pb2+ + 2e = Pb and 2l - 2e = l2
• Current and time
• 2160
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## Quantitive analysis & Ionic Equations - Questions

Quantative analysis

• What is a solute?
• How many grams of sodium are there in 25g of salt?
• You have a 10cm3 of a solution. You want to make it 10 times as dilute. How much water do you add?
• There is 1 mole of salt in 2dm3 of water. What is the concentration of the solution in mol/dm3?

Ionic Equations

• Write a word equation for the reaction of silver nitrate and sodium iodide.
• Why are sodium ions and  nitrate ions after spectator ions?
• Why do you wash a precipitate in distilled water when making a dry sample?
• Write an ionic equation for the reaction of silver nitrate and sodium bromide.
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## Quantitive analysis & Ionic Equations - Answers

Quantative analysis

• A substance that dissolves in a liquid.
• 15g.
• 90cm3
• 0.5

Ionic Equations

• Silver nitrate + sodium iodide = silver iodide + sodium nitrate
• If the solution used to make the precipitate was potassium nitrate instead of sodium nitrate the same precipitate would occur as sodium potassium and nitrate ions remain in solution.
• To remove traces of the solution filtered with the precipitate.
• Ag+ + Br- = AgBr
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## Titrations & Gas volumes - Questions

Titrations

• Alakli is slowly added to acid. How does the Ph change?
• If number of moles - concentration x volume in dm3, write down the relationship for concentration.
• Why are titration carried out several times before a volume is decided?
• 23.6 cm3 os a solution of 0.12 mol/dm3 hydrochloric acid react with 25.0 cm3 of sodium hydroxide colution. What is the concentration of the sodium hydroxide solution?

Gas Volumes

• A reaction gave off 96cm3 of sulfur dioxide. How may moles were made?
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## Titrations & Gas volumes - Answers

Titrations

• It increases
• Concentration = number of moles / volume
• To increase the reliability
• 0.113 mol/dm3

Gas volumes

• 17cm3
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## Equilibria & Strong and weak acids - Questions

Equilibria

• At equilibrium, the reaction A+B=C+D has 1 mole of A and B and 3 moles of C and D. Where is the position of the equilibrium?
• What happens to the equilibrium in the reaction of gases: N2+3H2=2NH3 is the pressure is increased?
• What are the conditions used in the Contact Process?
• Why is it called a compromise temperature in the Contact Process?

Strong and weak acids

• Strong acids break into their ions completely if put into water. What happens to weak acids when they are put into water?
• Explain why ethanoic acid is a weak acid.
• One ion makes a solution into an acid. Which one?
• Explain why strong acids react faster than weak acids.
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## Equilibria & Strong and weak acids - Answers

Equilibria

• To the right
• Moces to the right
• 450 Oc, atmospheric pressure, catalyst of vanadium pentoxide. V2O5.
• High temperature reduce the yielf of the reaction but the rate would be too low at low temperatures, so a somprimise is found, 450 Oc.

Strong and Weak acids

• Not all molecules seperate ions.
• The ionisation of ethanoic acid in water is not compelte. It is a reversible reaction where the position of equilibrium lies to the left.
• H+
• In strong acids the concentration of H+ is higher, so collision frequency is greater.
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