physical mock reviews

Question 1

whats the oxidation number of oxygen in hydrogen peroxide, H2O2.

Answer 1

-1

Question 2

ΔhydH⦵

Answer 2

enthalpy change when 1 moles of gaseous ions is dissolved in water

Question 3

draw an enthalpy cycle for calculating the enthalpy change of solution

Answer 3

Question 4

what are the 2 factors affecting enthalpy of hydration

Answer 4

1. ionic charge = higher charge -> more attraction to water molecules -> more energy released when bonds made -> more exothermic enthalpyof hydration
2. ionic radius = smaller ions higher charge density -> attract water molecules better -> more exothermic enthalpyof hydration

Question 5

define average bond enthalpy

Answer 5

energy need to break 1 mole of a bond in the gas phase, average over the different compounds that the bond is found in.

Question 6

how do you calculate bond enthalpy

Answer 6

total energy absorbed(bonds broken) - total energy released(bonds formed)

Question 7

whats the rate equation for A+B -> C+D

Answer 7

Rate = k[A]^m[B]ⁿ

^mn are the orders of reaction

Question 8

write K_p expression for aA+bB -> dD + eE

Answer 8

K_p = p(D)^dp(E)^e / p(A)^ap(B)^b

p=partial pressure

Question 9

state Le Chatelier’s principle

Answer 9

if theres a change in concentration, pressure or temperature, the equillibrium will move to help counteract the change.

Question 10

how will a change in pressure affect the equillibrium of a reversible reaction

Answer 10

increasing oressure will shift equillibrium towrads side wth fewer moles gas molceules to reduce pressure

Question 11

how do you calculate pK_a from K_a

and how would you caculate K_a from pK_a

Answer 11

pK_a = -log(Ka)

K_{a =} log₁₀^-pK_a

Question 12

how would you determine the % dissociation of an acid if you had the [H⁺]

Answer 12

[H⁺]/[A] x 100

Question 13

write the expression for K_w

Answer 13

Kw = [H⁺][OH^-]

Question 14

why do boiling points of halogens increase down the group

Answer 14

• increasing strength of london forces
• as number of electrons in increase when size and relative mass of atoms increases
• more energy needed to over come london forces

Question 15

% error formula =

Answer 15

(incertainty/reading) x100

Question 16

what are standard conditions when measuring electrode potentials using the standard hydrogen electrode

Answer 16

• ion solution 1 mol dm-3
• temp 295k (25°C)
• pressure 100kPa

Question 17

whats standard cell potential (e.m.f)

Answer 17

voltage between 2 half cells in an electrochemical cell

Question 19

how do you calculate the relative atomic mass from to isotopes in a sample

Answer 19

_{(relative isotopic mass x relative abundance of isotope Y) + (relative isotopic mass x relative abundance of isotope Z)} / 100

Question 20

first ionisation energies do what across a period

Answer 20

generally increase

however when a new subshell is reached the first element in the new block has lower i.e than the previous due to p orbital having slighlty higher energy than the s orbital so electrons are further from nucleus, as well as this there is additional shielding.

these factors overide the increase in nuclear charge

Question 21

define enthalpy change of neutralisation

Answer 21

enthalpy change when solutions of an acid and an alkali react together t form 1 mole of water, under standard conditions

Question 22

write the full balanced equation for complete neutrailisation of H₂SO₄ with NaOH

Answer 22

2NaOH + H₂SO₄ -> Na₂SO₄ + 2H₂O

Question 23

how do you caculate cell potential

E^⦵​_cell = ?

Answer 23

E^⦵​_cell = E^⦵_reduced - E^⦵_oxidised

Question 24

what are the angles in a complex ions with 6 ligands

Answer 24

90°