1) A 1.0 mL aliquot (sample) is taken from a 1.0L solution. Which of the followi

Question

1) A 1.0 mL aliquot (sample) is taken from a 1.0L solution. Which of the following is/are true when comparing the 1.0 mL solution to the 1.0L solution? Choose all that are true.

-The molarity of the 1.0 mL solution is less than the molarity of the 1.0L solution

-The molarity of each is the same

-The number of moles of solute in each solution is the same

-The number of moles of solute in the 1.0mL solution is less than the number of moles of solute in the 1.0 L solution

2) 5.00 mL is withdrawn from a 1.00L solution of NaCl and diluted to 100.00 mL. If the concentration of the NaCl in the 100.00 mL solution is 0.014, what is the concentration of NaCl in the original 1.00 L solution?

3) What is used as a blank (reference/zero absorbance) for the analysis of the samples in the spectrophotometer?

a) Deioniozed water

b) Nothing-air

c) Acetylsalicylic acid standard solution

d) Iron(III) chloride solution

4) The acetylsalycylic acid - iron (III) complex appears violet in color. What color of light is used to measure the absorbance of the solution?

a) red

b) orange

c) green

d) blue

e) violet

5) A calibration curve for absorbance versus the concentration of the chemical indicator crystal violet is found to have a slope of 61. If a sample of unknown concentration has an absorbance of 1.48, what is the concentration in the unknown sample?

Explanation / Answer

1) A 1.0 mL aliquot (sample) is taken from a 1.0L solution. Which of the following is/are true when comparing the 1.0 mL solution to the 1.0L solution? Choose all that are true.

-The molarity of the 1.0 mL solution is less than the molarity of the 1.0L solution --> False, concentration (molarity) is kept constant, does not vary on volume

-The molarity of each is the same - TRUE, as stated previously, the concnetraiton is kept constant

-The number of moles of solute in each solution is the same - FALSE, the amount of moles is dependent on volume

-The number of moles of solute in the 1.0mL solution is less than the number of moles of solute in the 1.0 L solution: This is false, since concentratino is kept constant, M = mol/V ... IF both, M and V are the same, mol must be the same

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