CI 1, 2, 3

Question 1

describe and explain the reactivity of nitrogen molecules

Answer 1

• They have a low reactivity
• Due to the strong triple bond holding the molecule together

Question 2

what is another name for ammonia (NH3)

Answer 2

nitrogen hydride (NH3)

Question 3

why can nitrogen hydride act as a base

Answer 3

• lone pair of electrons on the nitrogen allows dative covalent bond to be formed with the hydrogen ion

Question 4

with state symbols, what is the reaction for the production of ammonium

Answer 4

NH3 (g) + H+ (aq) —-> NH4 + (aq)

Question 5

give the appearance and formula of the following:
1. nitrogen oxide
2. nitrogen dioxide
3. dinitrogen oxide

Answer 5

1. NO - colourless gas (turns to brown NO2 in air)
2. NO2 - brown gas
3. N2O - colourless gas

Question 6

what is the equations for the following:
- the formation of nitrogen (II) oxide
- the formation of nitrogen (IV) oxide in air

Answer 6

• N2 (g) + O2 (g) —-> 2NO (g)
• 2NO (g) + O2 (g) —-> 2NO2 (g)

Question 7

what is the process of reduction of nitrogen (V) ions

Answer 7

NO3 - (aq) —> NO (g) —> N2O (g) —> N2 (g)

Question 8

give the chemical formula for
- nitrate (III)
- nitrate (V)

Answer 8

• NO2 -
• NO3 -

Question 9

draw the bonding of the following
- nitrate(III)
- nitrate(V)

Answer 9

NITRATE (III)
lone pair nitrogen electrons
|
O - single bond - N - double bond - O
NITRATE(V)
O - single bond - N - double bond - O
dative covalent bond
|
oxygen
pg. 287 in textbook

Question 10

how is nitrate(III) and nitrate(V) made

Answer 10

they are made through the oxidation of ammonium ions by anaerobic bacteria in the soil (so they can obtain respiration energy)

Question 11

how do you test for nitrate (V) ions

Answer 11

to test to test for nitrate (V) ions
- NO3 - ions, sodium hydroxide solution and devarda’s alloy are added to a test solution and gently heated.
- Aluminium acts as the reducing agent
- If the test solution contains nitrate (V) ions, ammonia gas will evolve

Question 12

how do you know that a gas is ammonia

Answer 12

• it has a sharp choking smell, and makes damp litmus paper turn blue
• forms white fumes of ammonium chloride when it comes into contact with hydrogen chloride gas from concentrated hydrochloric acid

Question 13

how do you test for ammonium ions (NH4 +)

Answer 13

• to test for NH4 + ions:
• sodium hydroxide solution is added to the test solution and gently heated
• if ammonium ions are present then ammonia gas will be given off

Question 14

what is the equilibrium concentration

Answer 14

• the concentration when the reaction has reached equilibrium

Question 15

what does an equilibrium constant of less than one tell you

Answer 15

• that a there is more reactants at equilibrium than products
• the reaction is incomplete

Question 16

what must you show with every Kc value

Answer 16

• the units
• the temperature for which it applies

Question 16

what is the rule about pressure for reversible reactions

Answer 16

• increasing the pressure moves the equilibrium to the side of fewer gas molecules

Question 17

why does Kc ALWAYS REMAIN CONSTANT, no matter what you do to the reaction, and provided that the temperature does not change (increase pressure etc.)

Answer 17

• because Le Chatelier’s principle states that the equilibrium always shifts to counteract the change in temp or pressure (…) as much as possible so the magnitude of Kc will remain constant

Question 18

which variable changes the value of Kc

Answer 18

• temperature

Question 19

if the forward reaction for a reversible reaction is endothermic, what would a rise in temperature do to the value of Kc

Answer 19

• a rise in temperature would favor the products and increase the value of Kc

Question 20

do catalysts affect the equilibrium constant

Answer 20

• NO they do not
• they alter the rate at which the equilibrium is attained, but not the composition of the mixture

Question 21

define rate of reaction

Answer 21

• the rate at which reactants are converted into products

Question 22

formula for rate of reaction

Answer 22

change in property/ time taken

Question 23

give examples of different properties you can measure to calculate the rate of reaction

Answer 23

• volume of gases evolved
• changes in mass
• pH measurement
• colorimetry
• chemical analysis using titration

Question 24

for the reaction of:
2 H2O2 —> 2 H2O + O2
- if the rate in terms of moles per second of water is 5 mol/s, what is the rate of formation of oxygen and why?

Answer 24

• ratio of moles of oxygen to moles to water is 2:1, so the rate of formation of moles of oxygen is 2.5 mol/s