rxn order graphs

[peyman2002]

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Could someone please tell me what the graphs for 1st,2nd and 3rd order rxns look like? they are confusing. some have Ln,some 1/[A] some just [A].

 

[PooyaH]

zero order:

[A] vs. time which has a negative slope (-k)

1st order:

ln [A] vs. time which has also has a negative slope (-k)

2nd order:

1 / [A] vs. time which has a positive slope (+k)

 

[IWantSmile]

• #1. If the reaction is zeroth (0th) order with respect to [X], which of the following quantities when plotted vs. t should be a straight line: ln [X], 1/[X], [X], or [X]2?
• #2. The half-lives for all first order reactions are independent of the initial concentration, true or false?
• #3. For a first order reaction, the product of rate constant and half-life is a constant. What is the constant? (give value)
  
• #4. Tritium (T) decays to helium (He of mass 3) with a half-life of 12.5 years. How long will it take 1.0 g of T to reduce to 0.25 g of T (and 0.75 g of He)?
• #5. The decomposition of HI is a classical second order reaction. 2 HI = H2 + I2(s). In an experiment starting at 8:00 hr, the partial pressure of HI decreases from 30.0 Pa to 15.0 Pa at 8:45 hr (at a constant temperature). What shall the time be for the partial pressure of HI to reduce to 3.75 Pa?
• #6. The dust explosion is a
  a. homogeneous reaction
  b. heterogeneous reaction
  c. catalytic reaction
  d. chain reaction
  
• #7. For the reaction: 2 NO + O2 -> 2 NO2, the following results were obtained: run [NO] [O2] Rate
  1 0.12 0.05 0.12
  2 0.12 0.10 0.24
  3 0.24 0.05 0.48
  What is the order of the reaction with respect to [NO]?
  What is the order with respect to [O2]?

 

[nze82]

Could someone please tell me what the graphs for 1st,2nd and 3rd order rxns look like? they are confusing. some have Ln,some 1/[A] some just [A].

ZERO ORDER:

FIRST ORDER:

SECOND ORDER:

 

[dentalaee]

Do we need to learn how to calculate this?

 

[nze82]

Do we need to learn how to calculate this?

Nope! But you need to know what each graph looks like.

 

[peyman2002]

so how about parabolic graphs of [A]?! how can I figure those kinda graphs out?
cause I've seen some A vs. T graphs that the slopes aren't straight lines

 

[nze82]

so how about parabolic graphs of [A]?! how can I figure those kinda graphs out?
cause I've seen some A vs. T graphs that the slopes aren't straight lines

The graph you're referring to corresponds to Nuclear Decay reactions, which are a special kind of 1st order reaction. So, just remember, if you see a greaph with a negative slope that looks like a parabola, it corresponds to a nuclear decay reaction.
Again, you're simply memorizing the shape of each graph and the reaction type it corresponds to. YOU'RE NOT REQUIRED TO CALCULATE AND/OR BE ABLE TO DRAW ANY OF THESE.

 

[Sublimation]

The graph you're referring to corresponds to Nuclear Decay reactions, which are a special kind of 1st order reaction. So, just remember, if you see a greaph with a negative slope that looks like a parabola, it corresponds to a nuclear decay reaction.
Again, you're simply memorizing the shape of each graph and the reaction type it corresponds to. YOU'RE NOT REQUIRED TO CALCULATE AND/OR BE ABLE TO DRAW ANY OF THESE.

I think i hit a question in destroyer about the decay of a second order reaction. I think with those every proceeding half like is double the first i think, or half of it. i cant remember

 

[nze82]

I think i hit a question in destroyer about the decay of a second order reaction. I think with those every proceeding half like is double the first i think, or half of it. i cant remember

Nuclear decay is without a doubt a FIRST ORDER REACTION.

 

[peyman2002]

yea I agree with nze82 nuclear decay is always 1st order rxn.
thanks for your help nze

 

[Sublimation]

yea I agree with nze82 nuclear decay is always 1st order rxn.
thanks for your help nze

The half life of first order reactions are always the same. 2nd order reactions half LIVES are always twice its predecessor for 2nd order reactions. .
.