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It is very desirable that pesticides eventually decompose in the environment to give harmless products. Let us assume the half life for the first order decomposition of a certain pesticide is 10.2 years. If the present concentration of a pesticide in a lake is 3.00x10^-3 M, what was the concentration 4.00 years ago?
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Half life= 10.2 years, t1/2= 0.693/k, k=0.693/10.2= 0.068
k=1/t*ln{[A0]/[A]}, but [A0]=? , [A]= 3* 10^-3, and t=4 years,
0.068= 1/4*ln{[A0]/3*10^-3}, this gives initial concentration [A0] = 3.94*10^-3M IMG_20150927_094710[1].jpg
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EQUIPMENT NEEDED:– AC/DC Electronics Lab Board: Capacitors, Resistors, Wire Leads – D-cell Battery –Digital Multimeter – Stopwatch or timer with 0.1 sec resolution.Purpose: The purpose of this lab will be to determine how capacitors behave in R-C circuits. The manner in which capacitors combine will also be studied.Experiment data: Your circuit board contains a battery, 2 resistors and 2 capacitors.Use the color code picture below to identify the resistors:2. Record in Table 1 the resistance of the resistors by the color code and due to color confusion, it would be wise to measure the resistance using a multimeter. This time, use the multimeter across each resistor, with the dial on the resistor scale (M?) and record in Table 1. Do not forget to convert from M? to k? (multiply by 1000).Table 1.ResistorColor CodeResistance by color code (k?)Resistance by using multimeter (k?)Resistor 1Red, red, yellow220210Resistor 2Brown, black, yellow100991003. Now take a look at the two capacitors placed on the circuit board. Read the valuewritten on them and record in Table 2.CapacitorCapacitance (µF)Capacitor 147Capacitor 2100Time constant ? is defined by the product between resistance and capacitor and it is measured in seconds.4. Use ? =RC and your knowledge of units for both resistor and capacitor, to prove that ? is measured in seconds. HINT: show how units cancels out and what is left is seconds.Show your work below:5. For Table 3, despite the fact that resistors and capacitor are given in k? and ?F, when you calculate the time constant ? you have to convert in ?and F. Table 3Resistor R (k?)Capacitor (?F)?=RC (s)Resistor 1= 220Capacitor 1=4710.34Resistor 2= 100Capacitor 1= 474.7Resistor 1= 220Capacitor 2= 10022Resistor 2= 100Capacitor 2= 10010Measure the voltage at the battery using the digital multimeter. Record the value below:?6. 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