a student dispensed 20.00 mL of 2x10^-5 M blue #1 solution into a test tube. He
ID: 793317 • Letter: A
Question
a student dispensed 20.00 mL of 2x10^-5 M blue #1 solution into a test tube. He then added 2.00 mL of NaCl solution and 2.00 mL of 2.50 % bleach solution.
a) calculate the molarity of the 2.50% bleach solution assume the density of the solution is 1.00g/mL
b) calculate the molarity of the bleach in the mixture(= blue#1 +Nacl+bleach)
* note that the molarity that is calculated in b) is the initial and constant molarity of the bleach in the experiment.
Please help me and explain and show your steps for each question
Explanation / Answer
(a) Consider 1.00 L = 1000 mL of bleach solution
Mass of solution = volume x density
= 1000 x 1.00 = 1000 g
Mass of NaClO = 2.50% of mass of solution
= 2.50/100 x 1000 = 25 g
Moles of NaClO = mass/molar mass of NaClO
= 25/74.44 = 0.336 mol
Molarity = moles/volume
= 0.336/1.00
= 0.336 M
(b) Moles of NaClO in mixture = 2.00/1000 x 0.336
= 0.000672 mol
Volume of mixture = 20.00 + 2.00 + 2.00 = 24.00 mL = 0.024 L
Molarity = moles/volume
= 0.000672/0.024
= 0.0280 M
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