1.2 amounts of substance part 2 Flashcards
what does stoichiometry tell you
the relative number of moles of reactant and products involved in a reaction
what is stoichiometry found from
the balanced equation
what is volumetric analysis used for
to find the volume of one solution which is needed to react with a measured volume of another solution
what can the results of volumetric analysis be used to find
the unknown concentration of one of the solutions
what is the solution with the known concentration called
the standard solution
the 4 steps to making a standard solution:
dissolve known mass of solid in de-ionised water
using a funnel, transfer into a volumetric flask; include washings
make up to the graduated line by carefully adding de-ionised water, making sure the meniscus sits on the line
stopper the flask and invert to mix the contents thoroughly
how to find the concentration of a solution of base
fill a burette with a known concentration of the acid
pipette a known volume of base into a conical flask
add a few drops of indicator to the base in the flask
add the solution of the acid from the burette until the indicator just changes colour- known as end point
record volume of acid added to nearest 0.05cm cubed
perform a rough titration and then sufficient accurate ones until the titres are concordant (within 0.01cm cubed of eachother)
calculate the mean titre from concordant titres to 2 d.p.
what colour is methyl orange in acid
red
what colour is methyl orange in base
yellow
what is methyl orange’s end point colour
orange
what colour is phenolphthalein in acid
colourless
what colour is phenolphthalein in base
pink
what is phenolphthalein’s end point colour
colourless
What are acid base titration calculations used for
To find the concentration of a solution of the volume of solution which reacts
What is a hydrated salt
A salt which contains water
What happens when hydrated salts are heated
The water is driven off and the compound is said to be anhydrous
What does waters of crystallisation refer to
The water molecules which form an essential part of the crystalline structure of a hydrated salt
How to calculate the number of moles of water of crystallisation
- you will need to know the masses of the hydrated and anhydrous salts
- mass of water = mass of hydrated salt - mass anhydrous salt
- work out the number of moles of anhydrous salt and of water
- find the simplest whole number ratio
What is percentage yield
A measure of the success of a laboratory preparation
How to work out percentage yield
Actual yield of product/theoretical yield of product x 100
Do both values need to be in moles for the percentage yield formula
Yes
What is theoretical yield
The number of moles expected if the reactants were completely converted into products
How to work out theoretical yield
Calculating the number of moles of reactants used and then using the balanced equation to calculate the number of moles of product if the yield was 100%
What is actual yield
The actual number of moles of product formed in the reaction
