chemical energetics

Question 1

exothermic reaction

Answer 1

a reaction that gives out energy

Question 2

endothermic reaction

Answer 2

a reaction that takes in energy

Question 3

enthalpy change

Answer 3

the difference in energy between the reactants and the products
relates to the change in thermal energy in the reaction

Question 4

what does a negative value for enthalpy change indicate

Answer 4

an exothermic reaction

Question 5

what does a positive value for enthalpy change indicate

Answer 5

an endothermic reaction

Question 6

enthalpy change formula

Answer 6

ΔH=energy of bonds broken – energy of bonds formed

Question 7

bond energy

Answer 7

the amount of energy in kJ/mol needed to break one mole of a bond

Question 8

to investigate the rate of reaction

Answer 8

• Measure the rate of appearance of products
• Measure the rate of disappearance of reactants
  rate=volume of gas in cm3/time in seconds

Question 9

factors affecting the rate of a reaction

Answer 9

• Concentration of solutions: increase in concentration= increase in rate of reaction
• Pressure of gases: increase in pressure= increase in rate of reaction
• Surface area: increase in surface area = increase in rate of reaction
• Temperature: increase in temperature = increase in rate of reaction
• Suitable catalyst = increase in rate of reaction

Question 10

What must happen for a successful chemical reaction to occur (collision theory)?

Answer 10

• The particles must collide
• The particles must collide with the correct orientation
• The particles must collide with sufficient kinetic energy (activation energy)

Question 11

A reversible reaction is at equilibrium when:

Answer 11

• The rate of the forward reaction equals the rate of the backward reaction
• The concentrations of reactants and products remain constant
• The reaction occurs in a closed system (when there is no exchange of substances with the surroundings

Question 12

If the concentration of the reactants increases… (equilibrium)

Answer 12

the equilibrium shifts to the right-hand side to remove the extra reactant that has been added causing an INCREASE IN YIELD OF PRODUCT

Question 13

If the concentration of the products increases… (equilibrium)

Answer 13

the equilibrium shifts to the left-hand side to remove the extra product that has been added causing a DECREASE IN YIELD OF PRODUCT

Question 14

If the pressure is increased.. (equilibrium)

Answer 14

the equilibrium shifts to the side with fewer mols, as this would reduce the overall pressure and restore the balance of equilibrium

Question 15

If the pressure is decreased (equilibrium)

Answer 15

the equilibrium shifts to the side with more mols, as this would increase the overall pressure and restore the balance of equilibrium

Question 16

increase in temperate (equilibrium)

Answer 16

moves to the endothermic reaction side

Question 17

decrease in temperature

Answer 17

moves to the exothermic side

Question 18

what is the haber process? + formula

Answer 18

• Industrial manufacture of ammonia from atmospheric nitrogen and hydrogen
• N2(g) + 3H2(g) ⇌ 2NH3(g)

Question 19

conditions for haber process

Answer 19

• 450 celcius
  
  • 200 atm
  • iron fillings as catalyst

Question 20

what is the contact process?

Answer 20

• The industrial process for producing sulfuric acid

Question 21

oxidation

Answer 21

the gain of oxygen or loss of electrons

Question 22

reduction

Answer 22

the loss of oxygen or gain of electrons

Question 23

Oxidising agent:

Answer 23

a substance that oxidizes another substance during a redox reaction while itself is reduced

Question 24

Reducing agent:

Answer 24

a substance that reduces another substance during a redox reaction while itself is oxidized