Moles Flashcards
To how many significant figures should your final answer be?
The same as the piece of data with the most significant figures
What do we call the number of moles?
The amount
Definition for amount of substance?
The quantity whose unit is the mole, used as a way of counting particles
Definition of a mole?
Amount of any substance, containing as many elementary particles as there are carbon atoms in 12g of Carbon 12. It contains 6.023 x10^23 atoms
Definition of Avagadro constant?
Number of elementary particles per mole of a substance= (6.02x10^23)
How to work out then amount of particles in a substance when given the moles?
Moles x 6.02x10^23= number of particles
How to work out the amount of moles present if given the amount of particles?
Amount of particles / 6.02x10^23
Formula linking moles, mass and molar mass?
Moles= mass/ molar mass
How do you find molar mass?
It’s the weight of the element
Definition of the empirical formula?
a formula giving the proportions of the elements present in a compound but not the actual numbers or arrangement of atoms.
How to work out the empirical formula of a compound
Divide the mass or percentage of each element in the compound by it’s molar mass.
Then divide these values by the smallest value there, to find the empirical formula
Definition of molecular formula?
a chemical formula that gives the total number of atoms of each element in each molecule of a substance
How to work out the molecular formula of a compound?
Add up the molar mass of all the elements in the compound, then divide the molar mass of the compound by this number. With this answer multiply the empirical formula to find the molecular formula
Definition of anhydrous?
Crystalline compound containing no water
Definition of hydrated?
Crystalline compound containing water
Definition of water of crystallisation?
water molecules forming an essential part of the crystal structure of some compounds.
How to find out how the ratio of anhydrous solid to water is in water of crystallisation?
Work out the moles of anhydrous solid
Work out moles of water
Look at ratio to see what number should go in front of water
Formula for percentage error?
Percentage error =Total uncertainty/ value measured then x100 for a percentage
How do you find out total uncertainty?
Add up all the possible errors in reading, eg. measuring scales only go to 2 d.p so there is a 0.005g error. So you can go each way so there is a 0.01g uncertainty.
What’s a procedural error?
When in the method things can occur which can change your final result, but it’s difficult to measure by how much
Method to finding reacting masses?
Write out balanced equation
Find the moles in which you are able to with the information given
Look at ratio and find moles of element/compound asked for
Use equations to answer question
Definition of a solute?
the minor component in a solution, dissolved in the solvent.
Definition of a solvent?
the liquid in which a solute is dissolved to form a solution
Definition of a solution?
a liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent).
Formula for concentration?
Concentration Moles/ dm^3= moles/ volume (dm^3)
How to convert cm^3 into dm^3?
Divide by 1000
In titrations what’s a concordant result?
Within 0.1 cm^3 pf another result
How to work out a concentration of an unknown acid using a titration?
Write equation
Work out moles of alkali
Look at ratio to find moles of acid
Use formula to work out concentration of acid
Formula for volume occupied by 1 mole of gas, at r.t.p?
Formula for volume occupied by 1 mole of gas (24dm^3)= mass of one mole/ density g dm^3
What’s the molar gas volume at r.t.p?
24 dm^3
Formula for volume of gas at r.t.p?
Volume of gas (dm^3)= moles x 24dm^3
How to calculate gas volumes using equations?
Write equation
Find moles of a known substance with information given
Use ratio to find moles of the gas your trying to find
Use equation to work out volume
What’s the ideal gas equation?
Pressure x Volume= number of moles x Ideal gas constant x temperature
In the ideal gas equation, what’s pressure measured in?
Pascals= Pa
In the ideal gas equation what’s volume measured in?
m^3
In the ideal gas equation what’s temperature measured in?
Kelvin
In the ideal gas equation what is “the amount measured in?
Moles
What’s the value of the ideal gas constant
8.314
How to solve ideal gas questions
Convert the values into their required form
Treat the equation like in maths to solve the unknown
How to convert degrees into kelvin?
Add 273
How to convert atmostpheres to pascals?
Multiply by 100,000
How to convert dm^3 to m^3?
Divide by 1000
How to convert cm^3 to m^3?
Divide by 1000 to get dm^3, then divide by 1000 again to get m^3
