1. Was the reaction zero, first, or second order, with respect to the concentration of crystal violet? Explain. 2. Calcu

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1. Was the reaction zero, first, or second order, with respect to the concentration of crystal violet? Explain. 2. Calculate the rate constant, k, using the slope of the linear regression line for your linear curve (k = -slope for zero and flst order and k = slope for second order). Be sure to include correct units for the mate constant Note: This constant is sometimes referred to as the pseudo rate constant, because it does not take into account the effect of the other reactant, OH-. Follow your teacher's instructions to share your value of the rate constant with the rest of the class, so they may use it in their error analysis. 3. Why was it necessary to record the room temperature when conducting this lab? I 4. Write the correct rate law expression for the reaction, in terms of crystal violet (ornitting OH-) 5. Why are we unconcemed with the rate of the reaction with respect to hydroxide in this experiment? Explain. 6. Using the printed data table, estimate the half-life of the reaction; select two points, one with an absorbance value that is about half of the other absorbance value. The time it takes the absorbance (or concentration) to be halved is known the half-life for the reaction. (As an alternative, you may choose to calculate the half-life from the rate constant, k, using the appropriate concentration-time fomnila.) Give this value with the appropriate units. 7. Write a conclusion including error analysis.

09 Zero Order 03 0.7 LINEAR 06 05 Hange: 0.2015 ym. - 001163 0.352 0.9912 RMSE 0.000306 04 03 02 01 100 150 200 250 300 @ First Order -12 LINLAR mange 0.2015 yeme.b he mc 0.005031 -0.0057 AMSE 0.002363 -10 100 150

Second Order LINEAR Range: 0-2013 yem.b M002293 b2336 T. 09919 RMSE 0.1754 3567 100 150 R

Lab: Rate Law Determination of the Crystal Violet Reaction In this experiment, you will observe the reaction between crystal violet and sodium hydroxide. One objective is to study the relationship between concentration of crystal violet and the time elapsed during the reaction. The equation for the reaction is shown here. HẠN NICH THÔN NỊCH, OH NCHƠI NGHI CV (violet color) CVOH (colorless) A simplified (and less intimidating!) version of the equation is: CVOH (aq) CV* (aq) (crystal violet) OH (aq) (hydroxide) The rate law for this reaction is in the form: rate= K[CV]"[OH-]", where k is the rate constant for the reaction, m is the order with respect to crystal violet (CV), and n is the order with respect to the hydroxide ion. Because the hydroxide ion concentration is more than 1000 times as large as the concentration of crystal violet, [OH-] will not change appreciably during this experiment. Thus, you will find the order with respect to crystal violet (m), but not the order with respect to hydroxide (n). +

As the reaction proceeds, a violet-colored reactant will be slowly changing to a colorless product. You will measure the color change with a colorimeter. The crystal violet solution used in this experiment has a violet color, of course, thus you will use the 565 nm (green) LED. We will assume that absorbance is proportional to the concentration of crystal violet (Beer's law). Absorbance will be used in place of concentration in plotting the following three graphs: Absorbance vs. time: A linear plot indicates a zero order reaction (k = -slope). In Absorbance vs. time: A linear plot indicates a first order reaction (k = -slope). 1/Absorbance vs. time: A linear plot indicates a second order reaction (k = slope). Once the order with respect to crystal violet has been determined, you will also be finding the rate constant, k, and the half-life for this reaction. OBJECTIVES . Observe the reaction between crystal violet and sodium hydroxide. Monitor the absorbance of the crystal violet solution with time. Graph absorbance vs. time, In absorbance vs. time, and 1/absorbance vs. time. Determine the order of the reaction.. • Determine the rate constant, k, and the half-life for this reaction.

Pre-loob Question The solution absorbs Yellow and queen wavelength and violet is reflected 1 2. cilesorbance cal comentation (M) % transmittance 0.000 015 0.010 .045 0.030 100.0 96.6 90.2 83.9 78.0 72,4 076 0.050 108 0.070 6.090 . 140 ce (6) A= abc .064 = { 1.001.042) {= 1.524 mol/cm- A = absorband E = molar absorptivity B = length of light push C = Concentration In [N: Os Jus time 3 (a) [Neg] is time [NO] us time (s)