Determining copper in brass

Assignment Help Chemistry

Reference no: EM13125497

Determining Copper in Brass
1st I titrated Na2S2O3 and determined the molarity to be 0.164. I am having trouble with the calculations for the dissolution of brass.

Method Weighed out 0.3026 g of an unknown barass, placed in a 250 mL Erlenmeyer flasks. In fume hood, add 5 mL of 6M HNO_3. Warm the solution on a hot plate until dissolution is complete. When dissolution is complete, add 10 mL of concentrated H_2 SO_4. Continue heating until SO_3fumes disappears. Cool flask for 2 minutes, place in an ice bath. Add 20 mL distilled water. Boil for 2 minutes, ice bath again, and dropwise add NH_3 (aq)until light blue turns dark blue.Add 3M H_2 SO_4 until dark color just disappears. Add 2mL of H_3 PO_4 to each sample. Cover with parafilm and set aside until ready for titration.
Then titrated the dissolved brass - Add 3.9853g KI and titrate immediately with Standard Thiosulfate solution. The color will first be brown or dark yellow-brown. Continue adding the standard thiosulfate solution until a light mustard color appears. Add 5 mL of starch indicator and titrate until color is a lavender-blue. Add 2.0099g of KSCN, mix well. The solution will darken. Continue titration until a white-cream color appears. This is the endpoint - it took 25.48 mL for the white color to emerge.

determine the Cu (%) in brass - I am confused what to calculate for the dissolved brass -
I got this so far -
.3026 brass (1 mol Cu/63.55 g Cu)(1 mol Cu2+/1 mol Cu)(1 mol I2/2 mol Cu2+)(2 mol S2O3/1 mol I2)/.02548 L

Reference no: EM13125497

Questions Cloud

Illustrate what is total amount of other financing source : Illustrate what is the total amount of other financing sources to be recognized on the fund-based financial statements over this six-year period?

Interest rate on the less expensive debt instrument : Alternatively, ABC can sell 9.5 percent coupon bonds with a 2-year maturity and $1,000 par value at a price of $950.00. How many percentage points lower is the interest rate on the less expensive debt instrument?

What is the ph after addition of hbr : A 100.0-mL buffer solution is 0.175M in HCIO and 0.150M in NaCIO .What is the pH after addition of 150.0mL of HBr?

Enough seats for all ticket holders who show for flight : What is the expected number of ticket holders that will fail to show for the flight? What is the probability that the airline will not have enough seats for all the ticket holders who show for the flight?

Determining copper in brass : Determining Copper in Brass, 1st I titrated Na2S2O3 and determined the molarity to be 0.164. I am having trouble with the calculations for the dissolution of brass.

Illustrate what adjusting journal entry must be made : illustrate what adjusting journal entry must be made to recognize bad debts expense on June 30, 2012?

How many grams of ethylene glycol must be added : How many grams of ethylene glycol C2H6O2 must be added to 1.15kg of water to produce a solution that freezes at -3.68 degrees celsius?

Probability to miss part of report if wait until grading : If the sports report begins at 11:10, what is the probability that he misses part of the report if he waits until grading is done before turning on the TV?

Explain important information about heat and temperature : Important information about Heat and temperature, What is Heat? What is temperature? What are the various properties that account for temperature?

User Account

All Pages