13531715
Description
Flashcards by I Shouldn't be awake, updated more than 1 year ago
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Created by I Shouldn't be awake
over 6 years ago
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| Question | Answer |
| Rate = | Δ%/t = ?moldm-3 |
| Zero order | Conc. of that reactant has NO effect on the rate |
| First order | Any change in conc. is mirrored in change of rate e.g. [A]^1 X 2 = rate X 2^1 |
| Second order | Any Δ in conc. causes the rate to increase by Δ^2 e.g. [A]^2 X 4 = Rate X 4^2 |
| Rate equation | Rate=k[A]m[B]n |
| Why would it be unlikely for X reaction to take place in 1 step looking at the rate equation? | Stoichiometry in reaction equation doesn't match the stoichiometry in the overall equation Collisions between more than 2 species unlikely |
| Overall order | overall effect of the [R]% on the rate sum of the powers |
| Rate constant K | Rearrange equation to make K the subject |
| K from overall order =1 | Rate=k[A]1 K=rate/[A]1 moldm-3s-1/moldm-3 K=moldm-3 |
| Methods to produce conc.-time graphs | Continuous monitoring via gas collection/mass loss/colorimetry |
| Analysis by Colorimetry (8) | 1. Prepare STD sol. of known % of coloured chemical. 2. Select a filter w/ comp. colour to coloured chem. 3. Zero the colorimeter with water 4. Measure the absorbance readings of the STD sol. 5. Plot a calibration curve of absorbance against %. 6. Carry out reaction, take absorbance readings at measured intervals. 7. Use the calibration curve to measure the conc. of coloured chem at each absorbance reading. 8. Plot a conc.-t graph to determine r.o.r |
| Purpose of calibration curve | Get concentration of reactant from absorbance reading |
| r.o.r from C-t graphs | Gradient |
| Orders from C-t graphs | Zero First |
| Zero order | Straight line w/ negative gradient R.O.R doesn't change during reaction |
| K from zero order reaction | K=gradient |
| First Order | Downward curve w/ decreasing gradient over time Constant t1/2 for [reactant] |
| t1/2 | t for [r] to halve from its original value |
| t1/2 First Order | Constant Shows Exponential Decay |
| K from First Order | K= ln2/t1/2 OR K= Rate(y/x)/[Reactant] |
| t1/2 from K | t1/2 = ln(2/k) |
| Rate-% graphs | Can be plotted for rate measurements at different concentrations |
| Orders from rate-% graphs | Zero - horizontal straight line w/ zero gradient r.o.r independent of conc. change |
| K from zero order reaction | r = K Intercept on Y axis gives K |
| First order | Straight line through origin |
| Rate from First Order rate-% | R=k[A] k = rate/% = Y/X |
| Second order graph | Upward curve w/ increasing gradient |
| Determing K from 2nd order rate-% graph | Plot 2nd graph of rate against [ ]^2 to get a straight line through origin Gradient of straight line = K |
| Clock reaction is a method of obtaining | IR by T for colour/precipitate formation |
| IR= | 1/t |
| Iodine clock colour change | Iodine w/ starch Colourless -> blue-black |
| Procedure | Keep [I-] constant, vary other [ ] Keep [I-] constant, vary [ ] Plot graph of 1/t against conc. |
| Rate-determining step | Slowest step |
| What species are included in the slowest step? | Species in the rate equation |
| What do the orders match? | The no. of species involved in the RDS |
| Hydrolysis of haloalkane | RBr + OH- --> ROH + Br- Step 1: RBr --> R+ + Br- Step 2: R+ + OH- --> ROH Step 3: RBr + OH- ---> ROH + Br- |
| Effect of T on rate constants | T ^ = Rate ^ = K^ |
| ^10c | For many reactions doubles r/k |
| Graph showing ^ effect | K T Upward curve |
| Effects of ^T (2) | ^T = Particles move faster, more collisions. ^T = More particles w/ Ea. |
| Arrhenius equation, exponential form | K=A e^-(Ea/RT) R=8.314 jmol-1k-1 |
| A | Factor that takes into account f of collisions w/ correct orientation |
| e^-Ea/RT | Proportion of particles w/ enough E to succeed Ea |
| Arrhenius equation - graphical form | lnK = -Ea/RT + lnA y = m x + c |
| Y = MX + C | Y = y axis X = x axis M = gradient C = intercept at Y |
| A | A = e^ln A |
| Ea | Ea * R |
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