inorganic chemistry practice errors

Question 1

explain in terms of equilibrium, why acidic conditions should not be used with cells containing CN- ions

Answer 1

H+ reacts with CN- to form HCN
so equilibrium shifts right and CN- is removed

Question 2

suggest three advantages of using ethanol rather than hydrogen in a fuel cell for vehicles

Answer 2

ethanol is less flammable than hydrogen
ethanol is less volatile than hydrogen
ethanol is easier to store

Question 3

define the term standard electrode potential

Answer 3

the electrode potential of a half cell compared to the standard hydrogen hal cell under standard conditions, i.e, 298K, 100KPa, and 1 moldm^-3

Question 4

state two ways that hydrogen can be stored as fuels for vehicles

Answer 4

it can be stored on a solid material
it can be stored within a solid material

it can be stored in liquid form AND under pressure

Question 5

state and explain the trend in atomic radius from Li to F (Li and F are in the same period)

Answer 5

atomic radius decreases because charge increases, due to the number of protons in the nucleus increasing

shielding stays the same

so there is a greater nuclear attraction between the outer shell electrons and the nucleus

Question 6

the equation between chlorine and sodium hydroxide to form bleach and the conditions required for this reaction to take place

Answer 6

2NaOH + Cl2 –> NaCl + NaClO +H2O

room temperature and dilute NaOH

Question 7

predict the structure and bonding of Barium Nitride

Answer 7

Giant ionic lattice

Question 8

describe the trend of first ionization energy across a period

Answer 8

across a period, the atomic radius decreases
inner shielding stays the same
so nuclear attraction increases, and more energy is required to remove an electron from the atoms in the period

Question 9

induced dipole-dipole forces act between which particles

Answer 9

molecules

Question 10

describe the general trend of atomic radius across period 3

Answer 10

atomic radius decreases across period 3

Question 11

why does magnesium have greater SECOND ionisation energy than strontium

Answer 11

Mg+ has a smaller ionic radius than Sr+

Mg+ experiences less shielding

so there is a greater nuclear attraction between the nucleus and outer electrons of Mg+ than Sr+

Question 12

why is the boiling point of PH3 lower than that of NH3 (both are in the same group)

Answer 12

NH3 has hydrogen bonding while PH3 does not

Hydrogen bond stronger than induced-dipole dipole forces in PH3, so more energy required to overcome the forces in NH3

Question 13

why is the boiling point of PH3 lower than the boiling point of AsH3 (As and P are all in the same group)

Answer 13

more electrons in AsH3 than PH3

so stronger induced dipole-dipole forces. therefore more energy is required to overcome the induced dipole-dipole interactions in AsH3

Question 14

entropy

Answer 14

a measure of the dispersal of energy and disorder within the chemicals making up a system

Question 15

formula for entropy

Answer 15

entropy of products- entropy of reactants

Question 16

transition metals with only one electron in their 4s subshell

Answer 16

copper and chromium

Question 17

explain how ligand substitution allows hemoglobin to transport oxygen in the blood

Answer 17

oxygen binds to the iron ion in hemoglobin

when oxygen is required, the bond breaks to release it

Question 18

formula for calculating bond enthalpies

Answer 18

The formula for calculating bond enthalpies is:

ΔH = Σ (bond enthalpies broken) - Σ (bond enthalpies formed)

where ΔH is the enthalpy change of the reaction, and Σ (bond enthalpies broken) and Σ (bond enthalpies formed) are the sums of the bond enthalpies of the bonds broken and formed, respectively.

Question 19

the standard state of iodine

Answer 19

The standard state of iodine is a solid at 25°C and a pressure of 1 atm. The standard state of an element is the physical state of the element at 25°C and a pressure of 1 atm. For iodine, the solid form is the most stable at room temperature and atmospheric pressure, and is therefore considered to be the standard state.

Question 20

what is the unit of k if ln2/ t1/2 is used to calculate the value of k

Answer 20

s^-1

Question 21

why do industries try to avoid increasing temperature to very high levels, in order to increase the yield of their products?

why do industries try to avoid decreasing pressure to very low levels, in order to increase the yield of their products

Answer 21

because high temperatures use large amounts of energy

low pressure gives a low rate of reaction, so the yield will be higher, but it will take much longer to produce the products

Question 22

why do industries avoid using high pressures to maximize the yield of their products

Answer 22

high-pressure systems can be expensive to build and maintain, so industries must balance the benefits of higher yield against the higher costs of production

Question 23

standard conditions required to measure the standard cell potential

Answer 23

298 K temperature
100Kpa pressure
1 mol per dm cubed of solution

Question 24

what colour is the [Cu(H2O)6]2+

Answer 24

pale blue solution

Question 25

when [Cu(H2O)6]2+ reacts with HCl, what does it form
what colour is this new solution

Answer 25

[Cu(Cl)4]2-

yellow solution

Question 26

[Cu(H2O)6]2+ reacts with KI to form

what are the colors of the individual products

Answer 26

CuI and I2

white solid for CuI

brown solution for I2

Question 27

[Cu(H2O)6]2+ reacted with NH3 forms

[Cu(H2O)6]2+ reacted with excess NH3 forms

Answer 27

[Cu(NH3)6]2+

[Cu(NH3)4 (H2O)2]2+

Question 28

an aqueous solution of ethanoic acid contains both hydrogen and hydroxide ions
how can an aqueous solution of acid contain hydroxide ions

Answer 28

water dissociates to form H+ and OH-

Question 29

for a buffer solution to form, what needs to be present in the buffer

Answer 29

an acid and it’s conjugate base

Question 30

bond enthalpy breaking of one mole of bonds in gaseous molecules

Question 31

Enthalpy change of solution

Answer 31

Enthalpy change required for 1 mole of ionic compound to fully dissolve in water

Question 32

Enthalpy change of solution

Answer 32

Enthalpy change required for 1 mole of ionic compound to fully dissolve in water

Question 33

Formula for enthalpy change of solution

Answer 33

Sum of hydration enthalpies - lattice enthalpy

Question 34

Average bond enthalpies

Answer 34

Average amount of energy required to break one mole of bonds in GASEOUS molecules

Question 35

Is activation energy ever negative

Answer 35

No

Question 36

Use of cis Platin In medicine

Answer 36

It is used in the treatment of cancer , although it has unpleasant side effects

Question 37

colour of these transition metal ions
V3+
V2+

Answer 37

green
violet