Topic 3 Quantative Chemistry

Question 1

What is the formula to calculate the % mass of an element in a compound?

Answer 1

Ar x number of atoms of that element /mr of compound x100

Question 2

What does avogadros constant mean?

Answer 2

Number of atoms, molecules or ions in mole of given substance

Question 3

What does concentration mean?

Answer 3

Amount of substance (mass or moles) in certain volume of solution

Question 4

What is the formula for concentration using the mass?

Answer 4

Concentration = mass of solute/volume of solvent

Question 5

What is the formula for concentration using moles?

Answer 5

Concentration = number moles of solute/volume of solvent

Question 6

What is atom economy a measure of?

Answer 6

Amount starting materials that end up as useful products

Question 7

What is the formula for atom economy?

Answer 7

Mr desired products/mr all reactants x100

Question 8

What is high atom economy better for?

Answer 8

Profits and environment

Question 9

What is the formula for percentage yield?

Answer 9

Percentage yield = mass products actually made/maximum theoretical mass products x100

Question 10

What are the 3 reasons yields are always less than 100%?

Answer 10

Side reactions
Not all reactants react to make product
Some product lost when separated from reaction mixture

Question 11

Why might not all reactants react to make a product?

Answer 11

Reversible reactions - products can turn back into reactants

Question 12

Why might there be side reactions during a reaction?

Answer 12

React with gases in air or impurities in reaction mixture- form extra products

Question 13

What are the 2 reasons industrial processes should have as high a percentage yield as possible?

Answer 13

Reduce waste
Reduce costs

Question 14

What are 2 reasons mass in a reaction would change?

Answer 14

Reactant is gas
Product is gas