Name: Chapter 9 Bonus Assignment CHEM1151L Section 093 Due: November 2, 2017 1.

Question

Name: Chapter 9 Bonus Assignment CHEM1151L Section 093 Due: November 2, 2017 1. You need to prepare a s0.00 ml solution of FD&C; Red Dye by diluting a concentration new diluted solution? You take 14.0 mL of the laboratory stock solution. What is the molarity of your 2. You have prepared 25.00 mL of a diluted FD&c; Red Dye solution that has a concentration of 425x make this solution you used 5.00 mL of a FD&C; Red Dye stock solution. What was the original concentration o the stock solution? 3. You have prepared 100.0 mL of a diluted FD&C; Red Dye solution that has a concentration of 7.75 x 10s M. The concentration of the stock solution of FD&C; Red Dye was 2.97 x 10 M. What volume of stock solution did you use to create your diluted solution? 4. You solution on t your percent error? are preparing he a diluted FD&C; Red Dye that should have a concentration of 3.85 x 10*M. After testing your spectrometer yo find your solution has an experimental concentration of 3.73 x 10* M. What is

Explanation / Answer

Q.

V = 50 mL rquired

C = 8.15*10^-6 M

if we need

V = 14 mL

Cfinal = ?

We need to apply dilution law, which is based on the mass conservation principle

initial mass = final mass

this apply for moles as weel ( if there is no reaction, which is the case )

mol of A initially = mol of A finally

or, for this case

moles of A in stock = moles of A in diluted solution

Recall that

mol of A = Molarity of A * Volume of A

then

moles of A in stock = moles of A in diluted solution

Molarity of A in stock * Volume of A in stock = Molarity of A in diluted solution* Volume of A in diluted solution

Now, substitute known data

then

C1*V1 = C2*V2

C2 = C1*V1/V2 = (8.15*10^-6)(14)/50

C = 0.000002282 M

C = 2.282*10-6 M

Q2.

V2 = 25 mL, C2 = 4.25*10^-5

V1 = 5 mL Cstock = ?

Cstock = 25/5*4.25*10^-5

Cstock = 0.0002125 M

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