Balanced equations and associated calculations Flashcards
Limiting Reactants and Excess, Reacting Mass Calcs. Percenatge Yield and Atom Economy
To calculate reacting mass calculations, what are the steps simply?
- Identify the mass of known elements
- Identify the Mr of the known elements
- Calculate the moles of the known elements
- Work backwards to find out whatever the question may have asked you
What is a limiting factor?
The limiting factor is a chemical that gets used up completely
What is the “excess”?
The excess is the chemical where there is more than enough of it, with some left over
What mass of calcium hydroxide is formed when 10g of calcium oxide reacts with 10g of water? ( CaO + H2O = Ca(OH)2 )
13.2g
What is the maximum mass of ammonium sulphate that can be obtained from 2kg of sulphuric acid and 1kg of ammonia? ( H2SO4 + 2 NH3 = (NH4)2SO4 )
2693.0g
What is the theoretical yield?
The theoretical yield is the largest amount of product that could be made, assuming there are no problems
What is the actual yield?
The actual yield is the amount of product actually made
What is percentage yield?
Percentage yield is a calculation to show how much (moles/mass) of what you could have made did you actually make
Why is the actual yield always less than the theoretical yield?
There can be anticipated human errors, equipment errors and also other more specific errors like chemicals reacting
How do you calculate percentage yield?
Percentage yield = (actual yield divided by theoretical yield) x 100
What is the percentage yield if 600g of ammonia is made from 1200g of nitrogen?
41.2%
What is atom economy?
The atom economy is the percentage value that indicates what % of our reactants are turned into useful products
What does a low atom economy indicate?
Low atom economy = an expensive and wasteful product
What does a high atom economy indicate?
A high atom economy indictaes less waste and fewer by products.
Calculate the atom economy to make calcium oxide from calcium carbonate. (CaCO3 = CaO + CO2)
56%
