the chemical industry
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What is the definition of reaction rate?
The change in the amount of reactants or products per time unit.
What are the ways of following the progress of a reaction?
pH measurement Gas volume Loss of mass Colorimetry Titration
How do you work out rate from a concentration-time graph?
Gradient = change in y/change in x Gradient represents rate
what assumptions do you make in the initial rate method of measuring rate?
• concentration of the other reactants isn’t changing significantly • temperature stays constant • the reaction has not proceeded too far
what is the rate equation?
rate=k[A]^m[B]^n
what does an order of reaction of 2 represent in terms of [A]?
[A] squared
define half life
the half life is the amount of time it takes for half of the reactants to be used up.
how does a zero order reaction present in terms of half life?
half life decreases with time
how does half life change for a 1st order reaction?
it remains constant
how does half life change during a 2nd order reaction?
it increases with time
how can you calculate the rate constant from half life?
k= ln2/half life
what must happen for a reaction to take place?
• particles must collide • have energy ≥ activation enthalpy • have the right orientation
how does increasing temperature affect the rate constant?
a higher temperature results in a higher rate constant
define order of reaction
order of reaction shows the number of molecules of that reactant which are involved in the rate determining step.
what economic considerations are there within the chemical industry?
• raw materials • overheads/fixed costs • fuel/energy • disposal costs
what alters the magnitude of Kc?
temperature changes; if the change in position of equilibrium results in more product, Kc is larger.
why is ammonia soluble?
can form hydrogen bonds with other molecules
what is a test for ammonium compounds?
• add NaOH + heat gently, ammonia gas should be evolved. - damp litmus -> blue
how do you test for Nitrate(V)?
warm solution with NaOH + add aluminium foil or devarda’s alloy. in the presence of an alkali, aluminium reduces nitrate -> ammonia gas.
describe the appearance and characteristics of the following oxides of nitrogen, NO, N2O and NO2
NO= colourless N2O= sweet smell, colourless NO2= brown, sharp odour, toxic
what are the equations for the conversion of N2 into NH3, and the conversion of NH3 into NH4?
N2 + 3H2 -> 2NH3 NH3 + H+ -> NH4+
what are the equations for the conversion of NH4+ into NO2-, and the conversion of NO2- into NO3-?
NH4+ +O2 -> NO2- +4H+ +2e- NO2+ + H2O -> NO3- + 2H+ + 2e-
what is the equation for the conversion of NO3 into N2?
2NO3+ 12H+ + 10e- -> N2 + 6H2O