Pc2 Topic Knowledge Flashcards
(24 cards)
What is the equation for percentage uncertainty
%uncertainty = uncertainty
/ ×100
Measured value
What could you do to reduce the percentage uncertainty
Use a larger mass
Use a mass balance with smaller uncertainty
Calculate number of particles
Number of moles× avogadros constan
Calculate the mass of 1 mole of particules
L X MASS OF ONE PARTICLE
Kpa to pa
×1000
Cm³ to m³
÷1×10⁶
Dm³ to m³
÷1×10³
What are the two assumptions we make about enthalpy change
The acid= water
All heat energy given off by the reaction is absorbed by the water in the acid
What is the equation for standard enthalpy of combination
H1 -H2
What is equation of enthalpy of formation
-h1+h2
Mean bond enthalpy
Reactant - products
Why might the ch4 bond be easily broken than Ch3
Ch4 is smaller than the bond angle Ch3
Larger repulsion between bonds in ch4 than ch3
Cause bond strength in Ch4 to be weaker
Suggest why enthalpy change calculated might be different to the data book
HEAT LOSS
INCOMPLETE COMBUSTION
How do you calculate water crystallisation
Mass of compound
Calculate mol of compound
Calculate mole of water crystallisation compound
Via 1: 1 ratio
Calculate mr of water crystallisation compound
Then use
Mr of wcc=compound Mr- x(18)
How to calculate back titration
Write out equation for both reactions a carried out
Identify key substance in both reactions
How much mole of hcl is in second reaction
How much mole of hcl is in first reaction
Take em away
Decribe the trend of ionisation across a period
Ionisation energy increases
Proton increase but the number of shells stay the same
Stronger attraction between nucleus and outer electron
Explain why 1 ionisation energy of Al is lower than mg
The outer electron in Al is in 3p
However in magnesium its outer electron is in 3s
3s is higher than 3p
3 p is further away for the nucleus than 3s
Suggest why oxygen has a lower ionisation energy than Nitrogen
2 electrons are paired in 2p
Pairing of electrons causes a greater repulsion
What is the equation for percentage yield
%yeild = actual
/ ×100
Theoretical
Why is percentage yeild never 100%
Some of the substance can get lost as its being transfer from beaker to beaker
What is the equation for atom economy
Atom economy =mass of desired product/ mass of total reactant × 100
Define ionisation energy
1 mole of an electron removed from ion mole of an atom to form one mole of gaseous ion
How do you know if a molecular is polar
If it has more than 2 atoms or It has a lone pair on its central atom
How do you know if a molecular is polar
If it has more than 2 atoms or It has a lone pair on its central atom
