Quantitative Chemistry Flashcards
What is the relative atomic mass of Carbon Dioxide?
C=12 O=16
12+16+16=44
How do you work out the percentage mass of an element in a compound?
Relative atomic mass x the number of atoms of that element / relative formula mass of that compound
How much will one mole of Carbon weigh?
the relative atomic mass of carbon is 12, one mole of something weighs the same as its atomic mass so it weighs 12g.
what is the formula to work out the number of moles in a given mass?
number of moles = mass in g / relative formula mas (Mr)
what is the conservation of mass rule?
during a chemical reaction, no atoms are created or destroyed.
True/False: the total Mr of all the reactants equals the total Mr of the products.
true
What are the two explanations for if the mass changes in a reaction (against the conservation of mass law)
- if the mass increases, one of the reactants is a gas that is found in the air and all the products are solids, liquids or aqueous
- if the mass decreases, one of the products is a gas and all the reactants are solids, liquid or aqueous.
what does aqueous mean
dissolved in water
What is the formula triangle that links mass, concentration and volume?
Mass on top
Concentration x volume on the bottom
How many cm cubed are in 1dm cubed
1000
What is the formula triangle that links moles, concentration and volume?
Moles on top
Concentration x volume on the bottom
How do you work out the percentage yield?
What you actually got
Divided by
What you thought you’d get
X 100
What are the three reasons for a chemical reaction not producing all the products you want it to?
Some reactions don’t go to completion because they are reversible
Some product may be lost when it is separated, eg left on the apparatus
Some of the reactants may react in different ways
The higher the yield the…
The more efficient the reaction
The more product is formed
The less waste is produced
The higher the profit for the manufacturer
What is yield?
The amount of product formed in a reaction
True of false: if there is only one product in the reaction, the atom economy is 100%
True
What is atom economy?
A mathematical way of explaining how good a reaction will be at making a useful product
What does a higher atom economy mean?
Lots of useful products
What does the atom economy do?
Compares the formula mass of the useful products with the formula mass of the reactants
How do you work out the % atom economy?
Sum of the Mr or useful products
Divided by
Sum of the Mr of all reactants
X 100
Why is atom economy important?
It shows is how much useful product we will get from a specific reaction and how much waste
Could be for economic reasons or sustainability
Helps scientist find best reaction pathway that will make the most useful products
What is the volume of one mole of any substance?
24 litres
What does the volume of a gas vary with?
The temperature and pressure
The higher the temperature of a gas, the ______ the volume
Greater
