Chemistry calculations

what is Avogadros constant

Formula for number of moles

6.02 × 10^ 23

𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 𝑛 = 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒𝑠 (𝑁) /
𝐴𝑣𝑜𝑔𝑎𝑑𝑟𝑜′𝑠 𝑛𝑢𝑚𝑏𝑒𝑟 (𝑁𝐴)

what is molar mass

what is the formula for molar mass (mr)

The molar mass is quite simply the mass of one mole of a substance.
• It has units of grams per mole (g/mol or gmol^-1)

𝑚𝑎𝑠𝑠 𝑚 = 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝐴𝑟 𝑜𝑟 𝑀𝑟 × 𝑚𝑜𝑙𝑒𝑠 (𝑛)

what is stoichiometry

The stoichiometry of a reaction is the molar ratio between the number of
moles of reactants and products in the reaction equation

when your calculating mass planning reactions what table is used

Mass

Mr

Moles

Molar ratio 

when you get moles you divide by your own column then multiply by how many 

what is the percentage yield formula

Actual yield or mass obtained / theoretical mass or theoretical yield x 100

what is the limiting reagent

how do you calculate the limiting reagent

the reactant that is completely used up

when you work out moles you divide both values by the smallest mole value

how to work out percentage yield of a reaction eg; C6H6 + I2 → C6H5I + HI Calculate the percentage yield for this reaction if 30.2 g of iodobenzene are obtained from 60 g of benzene and 60 g of iodine.

mass, mr, moles, ratio table

work out limiting reagent (smaller mole value out of benzene and iodine)

multiply mr of what you are trying to find with moles of limiting reagent

calculate percentage yield

what is molar volume (Vm)

𝑣𝑜𝑙𝑢𝑚𝑒 𝑉 = 𝑚𝑜𝑙𝑎𝑟 𝑣𝑜𝑙𝑢𝑚𝑒 𝑉𝑚 × 𝑚𝑜𝑙𝑒𝑠 (𝑛)

The molar volume (Vm) is the volume of one mole of a gas)

Vm = 24.0 dm3 at
Room Temperature (20 °C)
Room Pressure (1 atm)

Vm = 22.4 dm3 at
Standard Temperature (0 °C)
Standard Pressure (1 atm)

what is avogadros law

the volume of reactants is = to the volume of the products

what is Boyles law

if you halve the volume of a gas you double the pressure, they have an inverse relationship

PV = Constant

P1V1 =,P2V2

What is Charles law

if you increase the temperature of a gas, the volume increases

they are directly proportional

V/T = Constant

V1/T1 = V2/T2

What is the ideal gas law

PV = nRT

Pressure in pascals

Volume in metres cubed ³ (1m³, 1000dm³, 1,000,000cm³)

n = number of moles

R = gas constant = 8.314 J K-1 mol-1

T = Temperature in kelvin = + 273

How to go from m³ to dm³

Go from dm³ to cm³

Go from cm³ to dm³

Go from dm³ to m³

Formula for concentration with moles and volume

Concentration (C) = moles (n) / volume (dm³)

What is a titration

A technique used to work to work out concentration of a known substance

How does a titration work

1. You know volume and concentration do you can calculate moles

2. Calculate moles of second reagent from molar ratio

3. You know moles and volume so you can calculate C

What is Accuracy

What is precision

The closeness of agreement between final average result and value

Closeness of agreement between independent measurements

Percentage error formula

Accepted result - measured result / accepted result x100

3 types of error

Human, environmental, instrumental

Precision error calculation equation

%precision error = no. of readings x uncertainty/ measurement x 100%