Chemistry 1302A/B Lecture Notes - Lecture 3: Reaction Quotient, Nitrogen Fixation, Rhizobium

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blackraccoon59

2 May 2017

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Consider a chemical reaction, e. g. a b (1) So far we have mostly assumed that chemical reactions can only occur in one direction. However, realistically also the reverse reaction can occur. Will [a] go down to zero: no. Will [b] go down to zero: no. According to (1), there will always be some. We express the fact that the reaction can proceed in both directions by using the . This is read as a is in equilibrium with b . Because the reaction can proceed in both directions, an equilibrium will be established, where the concentrations [a] and [b] are in a fixed ratio. We call this ratio the equilibrium constant k. Example: assume k = 1, i. e. at equilibrium there will always be [b] = [a]. [b] = 4 equilibrium (= final) concentration (m) The value of k depends on the chemical nature of reactants and products, and on the temperature.

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Hi, I have a lab and have provided the information below and the data calculated at the end. Please help in prelab questions and postlab questions. WIll rate really good if it's correct. Thanks a lot.

DATA (The total liquid should be 50ml, not more than that)

SNO.	NACLO (intial temperature)	THE (B) Liquid temperature	NaClo(g)	The B solution(g)	FINAL temperature(together)
1	21.7	21.5	10ml	40ml	30.4
2	none	21.5	0ml	50ml	21.5
3	21.8	none	50ml	0ml	21.8
4	21.9	21.7	20ml	30ml	38.4
5	21.9	21.7	30ml	20ml	37.4
6	22.0	21.7	40ml	10ml	28.8
7	22.1	21.9	25ml	25ml	42.2

Mole ratio lab v3b Rukes APChemistry Determination of the mole ratio of a chemical reaction The method of continuous variations is a means of determining the stoichiometric mole ratio of the reactants in a chemical reaction. The stoichiometric ratio, as given by the coelficients in the balanced chemical equation, represents the ratio at which chemicals must be combined to produce al product with no excess rcactant. Sincc there is no âwasted" reactant, the maximum amount of product is made for the given amount of both reactants. In themethod of continuous variations, several trials are performed. In each trial, there is a fixed amount of total reactant (measured by moles or volume or mass, etc.), but with the two reactants mixed together in different ratios. Some measure of the amount of product is made for each trial (volumc of gas produccd, mass of precipitate, color of product solution, etc.). When the amount of product is maximized, the stoichiometric ratio has been used. A similar technique fixes the amount of one reactant and increases the other until the maximum amount of product is reached In this lab the two chemicals being mixed are solutions of known molarity. The total volume of solutions is kept constant over several trials. The chemicals will release heat when mixed together and raise the temperature of the mixture. Since the volume of the solutions mixed is held constant, the temperaturc changc recorded wl be proportional to the amount of heat produced and therefore also the "anount of reaction" that occurred. Objectives - To graphically determine the stoichiometric mole ratio of a reaction. CAUTIONS: All solutions are basic and can be harmful to skin and eyes. Sodium hypochlorite can also bleaclh clothing. Wear goggles, gloves and aprons. ï¸µ Pre-lab: complete on a separate sheet. 1. Accurately graph the following data gathered from an experiment which mixes 0.5 M solutions of AgNO3 and K2CrO4. The x-axis should plot the volume of AgNO3 reading Irom lef to right (or the volume of K2CrO4 reading from right to left.) Draw two best fit lincs, one for the "up" slope and one for the "down" slope... see example to the right of the data. (Also consult your graphing skills handout if you have not yet drawn a graph) trial mL AgNO3 mL K2CrO mass of precipitate (g) 45 35 25 20 15 10 shape of graph 15 25 30 35 40 45 5.0 4 10.0 9.9 6.6 3.3 a) Use the intersection of best fit lines to find the theoretical maximum amount of product. b) Use the x-values to find the stoichiometric volume ratio c) Use the answer from b) and given molarities to find the stoichiornetric mole ratio d) How many values were used to plot your "up" line? How many values were used to plot your "down" line? 2. What single temperature change should be recorded if 10 mL of solution A at 20Â°C is mixed with 10 mL of 3. What single temperature change should be recorded if 10 mL of solution A at 20Â°C is mixed with 30 mL of 4. List four dependent variables that are often used for the method of continuous variations. Are these enough values to plot a good line? solution B at 24.0Â°C and the final temperature reaches 28.0Â°C? solution B at 24.0Â°C and the final temperature reaches 28.0Â°C?

Chemistry 1302A/B Lecture Notes - Lecture 3: Reaction Quotient, Nitrogen Fixation, Rhizobium

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