Formulae , Equations and Amounts of substance Flashcards
Equations for the number particles
Number of particles = …
Number of particles = Avogardo number * moles
Equation for moles
Moles=…
Moles= Mass/RFM
Equation for number of moles
involving concentration and volume
Number of moles = concentration * volume
Equation for moles
includes volume and molar gas volume
Moles = volume / molar gas volume
Equation for concentration
includes mass and volume
Concentration = mass * volume
What’s the equation for ideal gas ?
pressure * volume = molesgas constant temperature
PV= nRT
What’s the equation for percentage error ?
Percentage error = uncertainty / reading * 100
What’s the equation for percentage yield ?
Percentage yield = actual yield / theoretical yield * 100
What’s the equation for % atom economy
% atom economy = Molecular mass of desired product / sum of molecular mass of all reactants * 100
What does the % atom economy tell us about the reaction
It tells us how efficient the reaction is
what is volume of 1 mole of gas
24 litres
What is Avogadro’s constant ?
6.02 x 10*23
What is a limiting reagent?
The one that runs out first
A+B -> C
moles of A = 1
moles of B = 2
What the moles of C and what’s the limiting reagent and what’s in excess ?
C=1 , A is the limiting reagent and B excess with 1 mole being left
3A + 2B -> 2C
moles of A = 3
moles of B = 3
What’s C and what’s the limiting reagent and what’s in excess ?
ratio between A and C of 3:2
divide A by 1.5 , C = 2
B is limiting and A is excess
What equation do you use when you have conc and vol before and after the reaction ?
Conc 1 * vol 1 = conc 2 * vol 2
What’s a titration and when would you use a titration ?
A titration is used to find a unknown concentration of solution by reacting it with a reactant with a known concentration
What is the empirical formula ?
The empirical formula is the smallest whole number ratio of the atoms of each element in a compound
Describe how you would find the empirical formula of a compound that has 27.3% carbon and 72.7% oxygen (mass)
- divide carbon by its % and RFM and do the same with oxygen
C = 27.3 / 12 = 2.3 , O = 72.7/16 = 4.5 - Divide each number by the smallest number
C= 2.3/2.3 =1 , O = 4.5/ 2.3 = 2 - this the ratio of the two numbers in the compound
CO2
What’s the molecular formula
shows the actual numbers of the atoms of each elements
What are spectator ions ?
Ions in an iconic compound that do not take part in a reaction
What are the steps for simplifying full iconic equations ?
- Start with the full equation
- Replace the formulae of ionic compound by their separate ions
- Cancel out any ions that appear identically on both sides
What is Avogadro’s law ?
States that equal volumes of gases under the same conditions of temperature and pressure contain the same numbers of molecules
Describe a outline of a titration
- Add the acid to the alkali until the equivalence point ( the point at which there are exactly the right amounts of substances) of the titration and the end point (the point where the indicator just changes colour ) has been reached
- Record the lowest part of the meniscus
- Record the titre
- repaet the titration until concordant titres are obtained
