C4-chemical Calculations Flashcards
How do you work out the relative formula mass
Add up the relative atomic masses of the elements in it, in the ratio shown by its formula
What the formula to work out moles
Number of moles=mass/formula mass
/ mass(g)/Mr
One mole of any substance is it’s relative formula mass, in grams
What is Avogadro constant
6.02 x 10^23
What is the limiting reactants
The reactant that gets used up first in a reacting. This is the reactant that is not in excess therefore the amount of products formed in a chemical reaction are determined by the limiting reactant
What is the equation for percentage yield?
Actual mass of product produced/maximum theoretical mass of product possible x100%
What is w yield of a chemical reaction
How much product is made
What are factors affecting the yield
Product being left behind in the apparatus
Reversible reactions not going to completion
Some reactants may produce unexpected reactions and losses in separating the products from the reaction mixture
Why is it important to maximise atom economy in industrial processes?
To conserve earths resources and minimise pollution
Formula for atom economy
Percentage atom economy = relative formula mass of the desired product from equation / sum of the relative formula masses of the reactants from equation
How can you increase the concentration of an aqueous solution?
You can add more solute and dissolve it in the same volume of its solution.
Evaporating off some of the water from the solution so you have the same mass of dilute in a smaller volume of solution.
Formula for concentration (g/dm^3)
Amount of solute (g)/volume of solution (dm^3)
What is titration used for?
Titration is used to measure accurately what volumes of acid and an alkali react together completely
What is the end point
The point at which a reaction between an acid and an alkali is complete is called the end point of the reaction. You can use acid/base indicator to show the end point of a reaction
Formula for moles
Moles =concentration x volume
What does one mole of any gas occupy a volume of (at room temperature and pressure?
24 dm^3
Room temperature =20degrees Celsius
Room pressure = 1 atmosphere
