So, I go to high school in Texas and we have this AP Chem lab due online tomorrow night by midnight and I need some serious help on these questions:
Lab Temp 0.2°C
Experiment Trial Time in seconds Trial 1 Trial 2 Average Time
1 1 2 256 275 268
2 1 2 215 226 220.5
3 1 2 83 59 71
4 Temp here is 35 ° C 1 83 Unnecessary
Initial concentrations:
Experiment [S203^2-] [S208^2-] [I-]
1 .0022 .0044 .2222
2 .0022 .0088 .2222
3 .0022 .0044 .4444
Initial rates from experiments 1,2, and 3 from [S2O3^2-] / ∆t:
Experiment [Na2S2O3] (M) Avg. Elapsed Time (s) ∆ Na2S203/ ∆t (M/s) ∆ S208^2-/ ∆ t (M/s)
1 .0022 268 8.2X10^-6 4.10*10^-6
2 .0022 220.5 9.97X10^-6 4.98X10^-9
3 .0022 71 3.10X10^-5 1.55X10^-5
Questions:
1. Determine the reaction orders to S2O8^2- using experiment 1 and experiment 2. Hint: Use m = log (rate 1/rate 2) divided by log (concentration 1/ concentration 2).
2. Determine the reaction orders to I- using experiment 1 with experiment 3. Hint: Use n = log (rate 1/rate 3) divided by log (concentration 1/ concentration 3).
3. What is the calculated rate law for this equation/reaction? Considering most rate orders have whole integers, what is most likely the correct rate law for this reaction?
4. Using the reaction rate calculated, calculate the rate constant for experiments 1, 2, and 3, and then the average rate constant for the three experiments.
5. Calculate the rate constant for experiment 4 at the elevated temperature.
6. Why are some reactions heated in laboratories?
I see no one has helped and that may be because all you need to do is follow the instructions in the problem. The hints tell you what to do. I suggest you do them. I'll be glad to answer specific questions about them. Post your work if you have further questions.
I figured out 1 and 2 but i don't understand how to do the rest
3. The rate law expression is
rate = k(S2O8^2-)x(I^-)y where x and Y are the orders of S2O8^2- and I^-. Plug in what you found for x and y and you have it. I don't know exactly what numbers you found but the question hints that they aren't whole numbers and suggests that you round them to whole numbers. The rate comes from the delta (...)/dT but I can't read what you have because of the spacing problem with this board.
4.
For 1 I got m is .282 and for 2 I got n is .53
I had to type it in word and it formatted fine even when i emailed it to myself. So how do you calculate the rate constant?
To help you answer these questions, you will need to use the provided data and apply some mathematical calculations. Here's how you can approach each question:
1. To determine the reaction orders with respect to S2O8^2-, you can use the formula: m = log (rate 1/rate 2) / log (concentration 1/concentration 2).
- Take experiment 1 and experiment 2, and substitute the given values into the formula to calculate the reaction order with respect to S2O8^2-.
2. To determine the reaction orders with respect to I-, you can use the formula: n = log (rate 1/rate 3) / log (concentration 1/concentration 3).
- Take experiment 1 and experiment 3, and substitute the given values into the formula to calculate the reaction order with respect to I-.
3. The rate law equation represents how the rate of the reaction depends on the concentrations of the reactants. It has the form: rate = k [S2O3^2-]^m [I-]^n.
- Use the calculated reaction orders from question 1 and question 2 as the respective exponents (m and n) in the rate law equation.
- Since rate orders usually have whole integers, round the calculated orders to the nearest whole number and write the balanced rate law equation.
4. The rate constant (k) represents the proportionality constant in the rate law equation. To calculate it:
- For each experiment (1, 2, and 3), divide the average rate (Δ[S2O3^2-]/Δt) by the molar concentration of S2O3^2-.
- Calculate the average rate constant by taking the average of the rate constants calculated from the three experiments.
5. To calculate the rate constant for experiment 4 at the elevated temperature:
- Use the Arrhenius equation, k = Ae^(-Ea/RT), where A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the temperature in Kelvin.
- Substitute the provided temperature into the equation and calculate the rate constant.
6. Reactions are often heated in laboratories for several reasons:
- Increasing the temperature can accelerate the rate of a reaction, allowing it to proceed more quickly.
- Heating may be necessary to provide the necessary energy (activation energy) for a particular reaction to occur.
- Some reactions are temperature-dependent, meaning they only proceed at certain temperatures or have different rates at different temperatures.
- Heating can also facilitate the evaporation of solvents or the removal of water molecules, favoring certain reactions.
Remember to double-check your calculations and units to ensure accurate answers. Good luck with your AP Chem lab!