2) 5.00 mL is withdrawn from a 1.00L solution of NaCl and diluted to 100.00 mL.

Question

2) 5.00 mL is withdrawn from a 1.00L solution of NaCl and diluted to 100.00 mL.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? Choose all that apply.

- Deioniozed water

- Nothing-air

- Acetylsalicylic acid standard solution

- Iron(III) chloride solution

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

-red

- orange

-green

-blue

-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

2) Final concentration of NaCl solution = 0.014 M

Final volume = 100 ml

molarity of initial 1.0 L solution = 0.014 M x 100 ml/5 ml = 0.28 M

3) Blank in the expeirment is,

Iron(III) chloride solution

-the acetylsalicylic acid-iron complex appears violet in color. The color used to measure the absorbance is,

blue

4) concentration = absorbance/slope

for the unknown,

concentration of unknown sample = 1.48/61 = 0.0243 M

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