C4 Quantative Chemistry Flashcards
What is Avogadro’s constant
The number of atoms, molecules, or ions in a mole of any substance
6.02 x 10^23
What is a burette
A tapped, glass apparatus used to add precisely known volumes of liquids to a solution
What is concentration
The abundance of solute in a solvent
What are concordant readings
Where tire values are within 0.1 cm3 of each other
These precise results can be used in accurate calculations
What is the end point
The point in a titration where the reaction is complete
What is a limiting reactant
The reactant in a chemical reaction that, when used up, causes the reaction to stop
This reactant is used up first
What is a mole
The amount of a substance in the relative mass of the substance in grams
What is percentage yeild
The mass of produce collected in a reaction as a percentage of the maximum mass that could have been formed in theory
What is a pipette
A glass apparatus used to measure accurate volumes of liquids
What is relative atomic mass (Ar)
The average mass of the atoms of an element in comparison to carbon-12
This takes into account the proportions of the naturally-occurring isotopes of the element
What is relative formula mass (Mr)
The total of the relative atomic masses, added up in the ratio shown in the chemical formula, of a substance
What is titration
A method used for finding the volumes of two solution that react together
What is yeild
The mass of product that a chemical reaction produces
What is the formula for moles
mass/Ar | mass/Mr
How are reactant masses calculated from equations
Find the Mr of the reactant and product in question
Divide the Mr’s by the Mr of the product to find how much reactant forms 1g of product
Multiply this by the amount of product in question to find how much reactant forms it
How are product masses calculated from equations
Find the Mr of the reactant and product in question
Divide the Mr’s by the Mr of the reactant to find how much product forms 1g of reactant
Multiply this by the amount of reactant in question to find how much product forms it
How are balanced equations written from masses
Find the moles of each substance
Divide each mol by the smallest mol
(If any numbers aren’t integers: multiply all values by the same amount so that they become whole numbers)
Write out the equation with these values in front of their according substances
How is product mass found from balanced equations and limiting reactant mass
Find the mol of substance with the known mass
Use the balanced equation to find how many mol of product the limiting reactant can form
Use mol to calculate mass
Why is percentage yield always <100%
Reactants may form unwanted products Product is lost in handling Reactants may not be pure Product is lost in separation processes Products may reform reactants (in reversible reactions)
Why is high percentage yield important`
Reduces waste Uses fewer reactants Uses less energy Increases profit Conserves raw materials Minimises costs
What is atom economy
The mass of the wanted product as a percentage of the mass of all the products
How is percentage yield maximised
Using the most efficient reaction conditions and apparatus
How is atom economy maximised
Using the most efficient reaction to make the wanted product
What is a standard solution
A solution of an accurately known concentration
What is the formula for concentration (g/dm3)
solute(g) / solution (dm3)
What is a decimeter
1 dm3 = 1000 cm3
To find decimetres, divide cm by 1000
To find centimetres, multiply dm by 1000
What happens in a titration
An acid and an alkali neutralise to form a salt and water
A known volume of alkali is put into a conical flask with an indicator
Acid is slowly added from a burette until the indicator shows that neutralisation has taken place
What is a titre
The exact volume of acid needed to neutralise an alkali
How is concentration calculated from titre values
Write out the balanced titration equation
Calculate the number of moles of the reactant with a known volume and concentration (in burette)
Use the equation to find the number of moles for the reactant with a known volume and unknown concentration (in pipette)
Use moles and volume to calculate the solution in the conical flask’s concentration
What is the volume of 1 mole of gas
24dm3 at room temperature and pressure, at 20C and 1 atmosphere
How many molecules does gas have under the same conditions
A certain volume of gas contains the same number of molecules under the dame conditions
What is the formula for moles of gas
dm3 / 24(dm3)
How can the volume of gases be calculated from balanced equations
The ratio of the number of moles in equation gives you the volume of gases involved.
