R2.1 How much, how fast and how far?

Question 1

what do chemical equations show

Answer 1

the ratio of reactants and products in a reaction

Question 2

what can the mole ratio of an equation be used to determine (mention 2 things)

Answer 2

• the masses and/or volumes of reactants and products
• the concentrations of reactants and products for reactions occurring in solution

Question 3

what does the limiting reactant determine

Answer 3

theoretical yield

Question 4

steps to find the limiting reactant

Answer 4

• find the moles of each substance
• divide moles by the coefficient in the equation
• lowest number = limiting reactant

Question 5

percentage yield

Answer 5

calculated from the ration of experimental yield to theoretical yield
% yield = (actual yield/theoretical yield) x 100

Question 6

actual yield

Answer 6

number of moles / mass of product obtained experimentally

Question 7

theoretical yield

Answer 7

number of moles / mass of product obtained by a reaction mass calculation

Question 8

factors which may stop all reactants forming products

Answer 8

• Other reactions occur simultaneously
• Reaction doesn’t go to completion
• Products lost during separation/purification

Question 9

atom economy, what is it, 2 circumstances where atom economy is 100%

Answer 9

A measure of efficiency
If there is only 1 product, atom economy = 100%
Addition reaction, atom economy = 100%
atom economy = (molecular mass of desired product/sum of molecular masses of all reactants) x 100

Question 10

factors affecting efficiency (apart from percentage yield & atom economy)

Answer 10

• rate
• quantities of reagents e.g. catalysts and solvents
• energy uses
• economic efficiency