In a reaction involving the iodination of acetone, the following volumes were used to make up the reaction mixture:
10 mL 5.0 M acetone + 10 mL 1.5 M HCl + 10 mL 0.005 M I2 + 20 mL H2O
A student found that it took 400 seconds for the color of the I2 to disappear.
a) How many moles of acetone were in the reaction mixture?
b) What was the molarity of acetone in the reaction mixture?
c) What was the rate of the reaction?
d) What was the rate of reaction?
A second reaction mixture was made up in the following:
20 mL 5.0 M acetone + 10 mL 1.5 M HCl + 10 mL 0.005 M I2 + 10 mL H2O
A student found that it took 100 seconds for the color of the I2 to disappear.
e) What were the initial concentration of each solution?
f) What was the rate of the reaction?
i) Write unknowns in either d or f, and calculate each unknown.
a) To determine the number of moles of acetone in the reaction mixture, we need to use the formula:
moles = volume (in L) x concentration (in M)
Given that the volume of acetone used is 10 mL (or 0.01 L) and the concentration of acetone is 5.0 M, we can calculate the number of moles of acetone:
moles of acetone = 0.01 L x 5.0 M = 0.05 moles
Therefore, there are 0.05 moles of acetone in the reaction mixture.
b) To find the molarity of acetone in the reaction mixture, we can use the formula:
molarity = moles / volume (in L)
Given that we previously calculated the moles of acetone as 0.05 moles and the total volume of the reaction mixture is 50 mL (or 0.05 L, since it is the sum of all the volumes used), we can calculate the molarity of acetone:
molarity of acetone = 0.05 moles / 0.05 L = 1.0 M
Therefore, the molarity of acetone in the reaction mixture is 1.0 M.
c) The rate of the reaction can be determined by calculating the change in concentration of iodine (I2) over time. Since the color of I2 disappears during the reaction, we can use the change in concentration of I2 to measure the rate.
Unfortunately, the information given does not include the concentrations of I2 before and after the reaction, so we cannot calculate the rate of the reaction.
d) This question is a duplicate of part c and does not provide any new information.
e) To determine the initial concentration of each solution in the second reaction mixture, we can use the volumes and concentrations given. The initial concentration is the concentration of the solution before any reaction occurs.
Given that the volume of acetone used is 20 mL (or 0.02 L) and the concentration of acetone is 5.0 M, the initial concentration of acetone is 5.0 M.
The volume of HCl used is 10 mL (or 0.01 L), and the concentration of HCl is 1.5 M. Therefore, the initial concentration of HCl is 1.5 M.
The volume of I2 solution used is 10 mL (or 0.01 L), and the concentration of I2 is 0.005 M. Hence, the initial concentration of I2 is 0.005 M.
The volume of water used is 10 mL (or 0.01 L), and there is no concentration associated with water since it does not participate in the reaction.
f) To calculate the rate of the reaction for the second reaction mixture, we need to know the change in concentration of iodine (I2) and the time taken for this change.
Given that it took 100 seconds for the color of I2 to disappear, we can use this value as the time taken for the change in I2 concentration.
Unfortunately, the information given does not include the concentrations of I2 before and after the reaction, so we cannot calculate the rate of the reaction.
i) There are no specific unknowns in either part d or f since they do not provide any new information to solve for unknown values.
To answer these questions, we need to use the concept of stoichiometry and the rate of reaction.
a) To find the number of moles of acetone in the reaction mixture, we need to use the volume and concentration of acetone. The given volume of acetone is 10 mL, and its concentration is 5.0 M.
Using the formula:
moles = volume (in L) x concentration (in mol/L)
We can convert the volume to liters by dividing it by 1000:
10 mL / 1000 = 0.01 L
Then, substitute the values into the formula:
moles = 0.01 L x 5.0 mol/L
Calculate the moles of acetone.
b) To find the molarity of acetone in the reaction mixture, we need to use the number of moles of acetone and the total volume of the reaction mixture. The total volume is the sum of all the volumes used to make the reaction mixture, which is 50 mL or 0.05 L.
Using the formula:
molarity = moles / volume (in L)
Substitute the values into the formula, using the calculated moles of acetone and the total volume of the reaction mixture.
c) The rate of the reaction can be determined from the rate equation or by monitoring the disappearance of a reactant or the appearance of a product over time. In this case, we are given the time it took for the color of I2 to disappear, which is 400 seconds for the first reaction and 100 seconds for the second reaction.
To determine the rate of the reaction, we can use the formula:
rate = change in concentration / change in time
Since the concentration of I2 is initially known and the change in concentration is zero (I2 disappears completely), the rate can be calculated as the initial concentration of I2 divided by the time taken.
d) The rate of reaction is the same as the rate determined in part c) since we are given the time it took for the color of I2 to disappear.
e) To find the initial concentration of each solution for the second reaction mixture, we need to consider the volume and concentration. The given concentration and volume values are the same as in the first mixture.
Using the formula mentioned in part b), calculate the molarity of acetone for the second reaction mixture.
f) The rate of the reaction can be determined using the same formula mentioned in part c), considering the time it took for the color of I2 to disappear in the second reaction.
i) To calculate the unknowns mentioned in parts d) and f), substitute the given values into the formulas and perform the necessary calculations.
A. mols acetone = M x L = ?
B. 5.00 M x (10 mL/total volume)= ?
C. final (I2) = 0.005M x (10 mL/total volume) = ?. Then rate rxn = final (I2)/400
D. repeat of C.
You should be able to use these numbers to do part B yourself.