Topic 3-Quantitave Chemistry Flashcards
(24 cards)
What is relative atomic mass?
The mass of all the atoms in the compound
How do you find the percentage mass of an element in a compound?
Ar of the element/Ar of the whole compound
What is a mole?
A mole is the name given to an amount of a substance
The Ar of the substance shows how much one mole of the substance weighs
Eg if a substance has an Ar of 12, that means that 1 mole weighs 12g
What is the formula to find the number of moles?
Mass
No of Mr
moles
What does the conservation of mass mean?
I’m a chemical reaction, mass is always conserved this means that no mass is created or destroyed so the mass at the beginning equals the mass at the end
Why might the mass change?
If there is a gas involved. The gas can either escape, or react to form part of the product
What is a limited reactant?
Reactions stop when one reactant is used up. Any other reactants are in excess.
The reactant rays used up is called the limiting reactant, because it limits the amount of product made.
The amount of product formed is directly proportional to the limiting reactant
How much does one mole of gas occupy? and at what temperature
24dm cube and 20degrees
What is the formula to find the volume of any gas?
Mass of the gas (g)/ Mr of the gas X24
What is concentration?
Concentration is the measure of how crowded things are. The more solute (substance dissolved) there is the more concentrated the solution is
What is the formula for concentration?
Mass of solute (g)
concentration Vol of solvent(dm3)
g/dm3
What are titrations?
Titrations are experiments that let you find out how much volume is needed for 2 solutions to fully react
What is the formula of concentration if you have Mol/dm3?
no.of moles
concentration Vol. of solvent
How do you convert mol/dm3 to g/dm3?
Use the mole equation
mass (g)=moles X mr
What is Atom economy?
The atom economy of a reaction tells you how much of the mass of the reactants is wasted and how much ends up as useful products
What is the equation for atom economy?
Atom economy %= Mass of desired products/ mass of all the reactants
If a reaction has 100% atom economy, what does it mean?
This means that all of the reactants in the reactions have been reacted into useful products.
The higher the atom economy, the greener the process
What is a high atom economy good for?
A high atom economy is good for profits and the environment.
If a reaction has a low atom economy, it is producing a lot of waste which damages the environment and isn’t profitable. or it isn’t sustainable
What is percentage yield?
Percentage yield shows how much product was made compared to how much was expected to be made.
Compares actual and theoretical yield
What is the formula for percentage yield?
= Actual yield / theoretical yield X100
^in g
What does 0% yield means?
That no product was made
Why do industrial processes need to have high percentage yield?
To reduce waste and costs
Why are yields always less than 100%?
Some product or reactant is always lost
What can go wrong in industrial processes?
Not all of the reactants react to make a product- in reversible reactions the product can go back to being reactants
There might be side reactions- the reactants might react with gases in the air or impurities in the mixture making extra product.
Some product might be lost when you separate it from the reaction mixture
