Topic 3 - Quantitative Chemistry Flashcards
What is the law of conservation of mass?
No atoms are lost or made during a chemical reaction
So mass of products = mass of reactants
Why do some reactions involve a change in mass?
A reactant or product is a gas and it’s mass has not been taken into account
What are chemical amounts measured in?
Moles
What is the mr or a substance equal to?
Mr = one mole of a substance in grams
What is the relationship between moles of different substances?
One mole of a substance contains the same number of particles as one mole of any other substance
What is Avogadro constant?
6.02 x 10 to the power of 23 per mole (the number of atoms in a given substance)
How do you calculate the balancing numbers in a symbol equation?
The masses of reactants and products
What is the limiting reactant?
Reactant that is completely used up because it limits the amount of products
Why is it not always possible to obtain to calculated amount of a product?
Reaction incomplete because it is reversible
Some of product lost when separated from reaction mixture
Some reactants May react differently to expected
What is yield?
The amount of product obtained
What is percentage yield?
The yield compared to the maximum theoretical amount as a percentage
What is atom economy?
A measure of the amount of starting materials that end up as useful products
Why is a higher atom economy important?
Costs less because less is wasted
Better for sustainable development
What conditions are needed for equal amounts in moles of gases to occupy the same volume?
Temperature and pressure must be the same
What is the volume of one mole of any gas at room temperature?
24 dm (cubed)
