chemistry - amounts

How do you convert from g to mg

multiply by 1000

How do you convert from g to Kg

÷ 1000

How do you convert from t to kg

x1000

How do you convert from m^3 to dm^3

x1000

How do you convert from cm^3 to dm^3

divide by 1000

Amount of substance

The quantity whose unit of the mole. Chemists use 'amount of substance' as a means of counting atoms.

Mole

Amount of substance containing as many particles as there are carbon atoms in 12g of carbon 12

Number of particles equation

Number of moles x Avogadro's constant

What is a particle

Can stand for atoms, molecules or ions

How does No of particles equation differ when its ions or atoms

Multiply by account of ions or atoms as well

Molar mass

Mass of one mole of a substance in g/mol.
Ar/ Mr

Mass equation 1

Mass (g) = moles x Ar or Mr

Density equation

Density (gcm^3) = mass(g) /volume (cm^3)

Molar gas volume

The volume per mole of gas molecules at room temperature and pressure (RTP)

What is room temperature and pressure?

298K and 100kPa/1

Volume equation at RTP

Volume (dm^3) = moles x 24

Ideal Gas Equation

PV=nRT
P = pressure Pa
V= volume m^3
n = number of moles
R = the molar gas constant
T = temperature K

How do you convert Celsius to Kelvin?

add 273

Molar equation 5

Moles = conc (moldm^3) x volume (dm^3)

Conc (gdm-3)

conc in moldm-3 x Mr

What is a limiting reactant?

the reactant that runs out first

Atom economy definition

A measure of the amount of starting materials that end up as useful products

How do you improve atom economy

By-products may be sold or used for other purposes, rather than sending them to landfill. This has 3 important benefits:
1) It costs less, as disposal can be expensive.
2) It is better for the environment so more sustainable as less landfill
3) less reactants so less use of finite resources

Atom economy equation

Mr of desired product/Mr of all products x100

Percentage yield

The percentage molar conversion of reactants to products

why is percentage yield never 100%

• incomplete reactions
• practical losses in transferring between equipment and washing/recrystalisation
• unwanted side reactions

Percentage yield

(actual yield/theoretical yield) x 100

Percentage purity formula

(actual mass/ mass of impure sample) x 100

anhydrous definition

A substance that contains no molecules of water of crystallisation.

hydrated definition

contains molecules of water of crystallisation

Water of crystallisation

Water chemically bonded within a crystal structure: the .xH20 part of the formula of a hydrated salt

How do you determine the Ar of magnesium

1. Set up the apparatus as shown. Using a measuring cylinder, add 10.0 cm³ of the 1.00 mol dm³ sulfuric acid (an excess) to the conical flask.

2. Weigh accurately between 0.12 g and 0.16 g of magnesium. Record the exact mass of magnesium using an appropriate format.

3. Remove the stopper, add the magnesium to the flask and quickly replace the stopper.

4. Collect the gas and record the final volume of hydrogen.

5. Assume room temperature and pressure.

Mg(s) + H2SO4(aq) → MgSO4(aq) + H2(g)