Amount of substance Flashcards
What is a mole?
Unit used to measure amount of substance
How many particles does one mole contain?
6.022 x 10^23
What is Avogrado’s constant?
6.022 x 10^23
What is the equation for number of particles?
Number of moles x Avogrado’s constant
What is the equation for number of moles in amount of substance?
Mass/ Mr
What is the equation for number of moles in solution?
Concentration x volume
What are the units for concentration?
moldm^-3
What are the units for volume?
dm^3
What is the ideal gas equation?
pV = nRT
What does the ideal gas equation allow you to do?
Find number of moles in certain volume of gas
What is p in the ideal gas equation and what is it measured in?
Pressure
Pascals
What is V in the ideal gas equation and what is it measured in?
Volume
m^3
What is n in the ideal gas equation and what is it measured in?
Number of moles
What is R in the ideal gas equation and what is it measured in?
8.32 JK^-1mol^-1
What is T in the ideal gas equation and what is it measured in?
temperature
Kelvin
How do you balance equations?
Work out how many of each atom you have on each side
What is included in the ionic equation?
Reacting particles and the products they form
What do you do after writing the ionic equation?
Ensure charges and atoms are balanced
What are the steps to making a standard solution?
1)Work out moles of NaOH you need (moles= conc x vol)
2)Work out grams of NaOH needed (mass = n x Mr)
3)Place weighing boat on digital balance and weigh out mass of solid. Tip into beaker. Reweight boat. Subtract mass of boat from mass of boat and solid together to find precise mass
4) Add distilled water to beaker and stir until all NaOH dissolved
5) Tip solution into volumetric flask. Use funnel
6)Rinse beaker and stirring rod with distilled water and add to flask too. This ensures no solute clinging to beaker or rod
7)Top flask to correct volume with more distilled water. Make sure the bottom of the meniscus reaches the line. When you get close to line add water drop by drop - otherwise have to start over
8)Stopper flask and turn it upside down a few time to make sure it is mixed
What is the purpose of a titration?
Allows you to find out exactly how much acid is needed to neutralise a measure quantity of alkali (or other way round). You can use this data to work out conc. of alkali
How is a titration set up?
1)Use pipette to measure out set volume of solution that you want to know conc. of and put in flask
2)Add a few drops of indicator
3)Fill burette with standard solution of acid
4)Use funnel to carefully pour acid into burette. Do this below eye level to avoid any splashing on your face and eyes
How do you carry out a titration?
1)Do rough titration to get idea of end point. Add acid to alkali using burette, giving flask regular swirl
2)Now do accurate titration. Take an initial reading to see exactly how much acid is in burette. Then run the acid in to withing 2cm^3 of the end point. Then add it dropwise
3)Work out the amount of acid used to neutralise the alkali. Final reading-initial reading. This volume is known as the titre
4)Repeat a few times until you have concordant results
5)Use results from each repeat to calculate mean volume of acid used
What colour is phenolphthalein in acid and alkali?
Colourless in acid
Pink in alkali
What is empirical formula?
Simplest whole number ratio of atoms of each element in a compound
What is molecular formula?
Actual numbers of atoms of each element in a compound
Made up of a whole number of empirical units
What is theoretical yield?
Mass of product that should be formed in a chemical reaction.
What does theoretical yield assume?
That no chemicals are “lost” in the process
How do you calculate theoretical yield for a reaction?
Use the mass of reactant and a balanced equation
What is the equation for percentage yield?
(actual yield / theoretical yield) x 100
What does percentage yield measure?
How wasteful a process is - based on how much of the product is lost during the process
What is atom economy?
A measure of the proportion of reactant atoms that become part of the desired product rather than by-products in the balanced chemical equation
What is the equation for atom economy?
(molecular mass of desired product / sum of molecular masses of all reactants) x 100
State three benefits for companies trying to use processes of high atom economy?
Better for environment
Make more efficient use of raw materials
Less expensive
Why are processes with high atom economies better for the environment?
Produce less wate
Why are processes with high atom economy good for using raw materials?
More sustainable as they use up natural resources more slowly
Why are processes that use high atom economy less expensive?
Spend less on separating desired product from waste products and less on treating waste
