chem Kinetics and equili

Question 1

What is the chemical kinetics concerned with?

Answer 1

-speeds, or rates of reactions

Question 2

Name the facts affecting rates of chemical reactions?

Answer 2

• The concentrations of the reactants
• The temperature at which the reaction occurs
• The presence of a catalyst (such as enzymes)
• The surface area of solid or liquid reactants or catalysts

Question 3

How can you measure the reaction rate?

Answer 3

• Average rate = change in the number of moles of B / change in time
• Average rate = change in the number of moles of A / change in time
• A —>B

Question 4

Give the first order reaction for A—> products

Answer 4

• a first-order reaction has a rate proportional to the concentration of one reactant
• Rate = k[A]
• Rate is how quickly they disappear over time
• k is the rate constant
• k[A] is the concentration of A

Question 5

Give the second order reaction for A—> products

Answer 5

• a second-order reaction has a rate proportional to the product of the concentrations of two reactants, or to the square of the concentration of a single reactant
• Rate = k[A]2

Question 6

What is the relationship between temperature and rate?

Answer 6

• rates of most chemical reactions increase as the temperature rises
• (is initially faster)

Question 7

Define chemical equilibrium

Answer 7

• the condition in which the concentration of all reactants and products in a closed system cease (aufhören) to change with time
• when the rates are equal

Question 8

How is the equilibrium constant calculated? For: aA+bB —>

Answer 8

• Kc = [C]^c* [D]^d/[A]â*[B]^b
• [A] = concentration of A in mol dm^-3
• a= number of moles of A

Question 9

What does it mean if K is bigger/smaller than one?

Answer 9

• k>1 = more products than reactants at equilibrium, and the equilibrium is said to lie to the right
• k<1 = more reactants than products at equilibrium, and the equilibrium is said to lie to the left

Question 10

Define the principle of Le Chatelier

Answer 10

-«If a system at equilibrium is disturbed by a change in temperature, pressure, or the concentration of one of the components, the system will shift its equilibirium position so as to counteract the effect of the disturbance.»

Question 11

What happens if we add or remove substance from the equilibrium reaction?

Answer 11

• add= the reaction will shift so as to reestablish equilibrium by consuming part of the added substance
• removal= result in the reaction moving in the direction that forms more of the substance

Question 12

Which effects do the volume and pressure have on equilibrium reaction?

Answer 12

-Reducing the volume of a gaseous equilibrium mixture causes the system to shift in the direction that reduces the number of moles of gas

Question 13

Which effects does temperature have on equilibrium reaction?

Answer 13

• Almost every equilibrium constant changes in value as the temperature changes
• When the temperature is increased, the equilibrium shifts in the direction that absorbs heat
• Endothermic (100= heat goes to the side of reactant) : Increasing T results in an increase in K
• Exothermic (-100= heat goes to the side of product): Increasing T results in a decrease in K