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
what is the meniscus ?
the curving of the upper surface in a liquid in a container , should read the lowest part of the meniscus
What is a titre ?
the volume added from the burette during a titration
What is the concordant titres ?
titres that are close together ( usually titres of 0.1 - 0.20 cm3)
What is a precipitation reaction ?
reactions in which an insoluble soild is one of the products
What are the 5 equations for the reactions between acid and metals ?
- Metal + acid -> salt + hydrogen
- Metal oxide + acid -> salt + water
- Metal hydroxide + acid -> salt + water
- Metal hydroxide + acid -> salt + water
- Metal carbonate + acid -> salt + water + carbon dioxide
What happens when a metal hydrogen carbonate reacts with a acid ?
-Use the example of sodium hydrogencarbonate and citric acid
Sodium hydrogencarbonate + citric acid -> sodium citrate + water + carbon dioxide
Define accuracy
A measure of the closeness of agreement between an individual result and the accepted value
Definition of precision
The closeness of the values obtained between independent measurements obtained under the same conditions
Definition of uncertainty
An estimate attached to a measurement based on range the true value could be in
Definition of reliability
The opposite of uncertainty , high uncertainty = not very reliable
