1) In order to understand how this equation is derived and why it holds true, th
ID: 1043338 • Letter: 1
Question
1) In order to understand how this equation is derived and why it holds true, the product of each side of the equation should be examined. What value and unit do you get when you multiply a concentration of 0.767 M by a volume of 0.650 L ? This question can be expressed as
0.650 L1×0.767 molL=
Express your answer to three significant figures with the appropriate units.
2)When you need to produce a variety of diluted solutions of a solute, you can dilute a series of stock solutions. A stock solution has a significantly higher concentration of the given solute (typically
101to 104 times higher than those of the diluted solutions). The high concentration allows many diluted solutions to be prepared using minimal amounts of the stock solution.
What volume of a 6.25 M stock solution do you need to prepare 250. mL of a 0.0900 M solution of HNO3?
Express the volume to three significant figures with the appropriate units.
3The absorbance of a cationic iron(II) sample solution was measured in a spectrophotometer, but the instrument returned an error because the absorbance was too high. The sample was then diluted by using a pipette to take 100.0
?L of the sample and injecting it into a cuvette already containing 2.00 mL of water (total volume is 2.00 mL + 100.0 ?L). The absorbance value of the diluted solution corresponded to a concentration of 9.38×10?6 M . What was the concentration of the original solution?
Express the concentration to three significant figures with the appropriate units.
Explanation / Answer
1.
Moles = 0.650 L * 0.767 mol/L = 0.498 mol
2.
Dilution formula,
M1 * V1 = M2 * V2
6.25 * V1 = 0.0900 * 250.
V1 = 3.60 mL of stock is tob taken and it is diluted to 250. mL to get 0.0900 M solution
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