Ch. 3.4 : Reacting Quantities Flashcards
What are balanced equations used to find?
The quantities of reactants required to prepare a required quantity of a product
The quantities of products that should be formed from certain quantities of reactants
How do you find how much of something reacts in a given reaction?
Step 1 : work out the amount in moles of whatever you can
Step 2 : use the balanced equation to work out the amount in moles of the unknown chemical
Step 3 : work out the unknown information required
How do you identify a metal ?
Step 1 : calculate the amount of gas produced in moles
Step 2 : From the equation and the result from step 1, the moles of the metal can be determined
Step 3 : work out the unknown information
Why is it difficult to reach theoretical yield?
The reaction may not have gone to completion
Other reactions ( side reactions ) may have taken place alongside the main reaction
Purification of the product may result in loss of some product
How do you work out percentage yield?
Actual yield / theoretical yield x 100
What is the limiting reagent?
The reactant that is not in excess that will be completely used up first and stop the reaction
How do you work out the limiting reagent?
Working out the amount in moles of each reactant and comparing with the equation.
What is atom economy?
A measure of how well atoms have been utilised
Describe reactions with high atom economies
They produce a large proportion of desired products and few unwanted waste products
They are important for sustainability as they make the best use of natural resources
How do you work out atom economy ?
Molar mass of desired products / molar mass of all products x 100
