Equilibria Flashcards
Sulfuric acid is manufactured by the Contact Process.In this process, sulfur dioxide reacts with oxygen. The equation for the equilibrium that is established isSO2(g) + 1/2O2(g) SO3(g) ΔH = –98kJmolState and explain the effect of a decrease in temperature on the equilibrium yield of SO3and why?
(Yield) increases / goes up / gets moreThe (forward) reaction / to the right is exothermic or gives out / releases heatOR The reverse reaction / to the left is endothermic or takes in /absorbs heatThe (position of ) equilibrium shifts / moves left to right to oppose the decrease in temperature
Give two features of a reaction at equilibrium
- Concentration(s) (of reactants and products) remain or stay constant / the same2. Forward rate = reverse / backward rate
Write an equation for the reaction of concentrated sulfuric acid with potassium bromide to form potassium hydrogensulfate and hydrogen bromide.
KBr + H2SO4 ——>KHSO4 + HBr
Bromine is one of the products formed when concentrated sulfuric acid reacts with hydrogen bromide.Write an equation for this reaction.State the role of sulfuric acid in this reaction.
2HBr + H2SO4 ——>Br2 + SO2 + 2H2OOxiding agent or electron acceptor or oxidanti.e. to oxidise the bromide ion
Concentrated sulfuric acid is used in a two-stage process to convert 2-methylpropene into 2-methylpropan-2-ol.Stage 1 (CH3)2C CH2 + H2SO4 —–>(CH3)2C(OSO2OH)CH3 Stage 2 (CH3)2C(OSO2OH)CH£ + H2O —–>(CH3)2C(OH)CH3 + H2SO4Name this type of conversion in stage 1 and 2State the overall role of sulfuric acid in this conversion.
- Electrophilic addition2.Hydrolysis3. Catalyst
State the meaning of the term rate of reaction.
Change in concentration of a substance / reactant / product in unit time
Hydrogen gas is collected when a sample of magnesium reacted with an excess of dilute hydrochloric acid.The rate of this reaction can be studied by measuring the time it takes for a given volume of hydrogen to be collected. In terms of collision theory explain why, at a fixed temperature, the rate of this reaction doubles when the concentration of the hydrochloric acid doubles.
Twice / double as many particles / hydrogen ions (in a given volume) causes twice / double as many effective / successful collisions (in a given time)
State the meaning of the term activation energy.
The activation energy is the minimum energy for a reaction to start
A study of equilibrium is important for understanding chemical reactions.State Le Chatelier’s principle.
(When a system / reaction in equilibrium is disturbed), the (position of) equilibrium shifts / moves in a direction which tends to reduce the disturbance
State the meaning of the term catalyst. Explain, in general terms, how catalysts work.
A substance that speeds up the reaction / alters the rate but is chemically unchanged at the end / not used upCatalysts provide an alternative route / alternative pathway / different mechanismthat has a lower activation energy / Ea ORlowers the activation energy / Ea
State the effect, if any, of a catalyst on the time taken to reach equilibrium.
(Time is) less / shorter / decreases / reduces
State the effect, if any, of a catalyst on the position of an equilibrium.
None
Ammonia is manufactured by the Haber process in which the following equilibrium isestablished.N2(g) + 3H2(g) 2NH3(g)Give two features of a reaction at equilibrium.
Concentrations (of reactants and products) remain or stayconstant / the same Forward rate = Reverse / backward rate
Explain why a catalyst has no effect on the position of an equilibrium.
Catalysts increase rate of / speed up both forward andreverse / backward reactionsincrease in rate / affect on rate / speed is equal / the same
A sample of nitrogen dioxide gas (NO2) was prepared by the reaction of copper with concentrated nitric acid.Balance the equation for the reaction of copper with concentrated nitric acid. Cu + …….. HNO3 ———->Cu(NO3)2 + …….. NO2 + …….. H2O
Cu + 4HNO3 ———->Cu(NO3)2 + 2NO2 + 2H2O