Topic 5 - Separate chemistry 1

Question 1

How can you calculate the molar volume of a gas

Answer 1

Molar volume = volume (dm^3) / moles of gas
Unit - dm^3 mol^-1

Question 2

What is atom economy?

Answer 2

Measure of the efficiency of the reaction, looks at amount of reactants that get turned into useful products

Question 3

How can you convert concentration from g dm^-3 to mol^-3?

Answer 3

Concentration (mol dm-3) = concentration (g dm^-3) / molecular mass (Mr)

Question 4

How do you calculate the concentration of a solution in g dm^-3?

Answer 4

Concentration (g dm^-3)
= mass (g) / volume (dm3)

Question 5

How do you calculate the concentration of a solution in
mol dm^-3?

Answer 5

Concentration (mol dm^-3)
= moles / volume (dm3)

Question 6

Why might a specific reaction pathway be chosed over another

Answer 6

• Higher atom economy
• Higher yield
• Faster rate
• Equilibrium position favours products more
• By-products are more useful or less harmful

Question 7

What is the percentage yield of NH3if 40.5g of NH3 is produced from 20.0 mol H2 and excess N2?

Answer 7

Equation: N2+ 3H2 –> 2NH3
Moles of ammonia = 20/1.5 = 13.3 moles
Mass of ammonia = 13.3 x (14+1+1+!) = 227g
Percentage yield = (40.5/227 )x 100 = 17.8%

Question 8

How do you convert concentration from g dm^-3 to mol dm^-3?

Answer 8

Concentration (g dm^-3) = concentration (mol dm^-3) x molecular mass (Mr)

Question 9

What os the molar volume of a gas at room temperature and pressure?

Answer 9

The volume occupied by one mole of molecules of any gas at room temperature and pressure

Question 10

Fill in the gap: ‘The ______ the atom economy, the more sustainable and efficient the process’

Answer 10

The higher the atom economy, the more sustainable and efficient the process

Question 11

What is room temperature and pressure?

Answer 11

Room temperature - 20C
Room pressure - 1 atmoshpere

Question 12

How do you calculate atom economy?

Answer 12

Atom economy = (Mr of desired product / Mr of reactants) x 100

Question 13

How do you calculate percentage yield?

Answer 13

Percentage yield = (Actual yield / Theoretical yield) x 100

Question 14

What does Avogadro’s Law state about gas volumes?

Answer 14

At the same temperature and pressure, equal amounts of gas will occupy the same volume

Question 15

Why could the actual yield of product be less than the theoretical yield?

Answer 15

• Incomplete reaction
• Practical losses during experiment (e.g. some solid may get lost when being transferred between beakers)
• Cometing, unwanted reactions (side reactions)