Chemistry Questions and Answers October 04, 2019

Consider the titration described here: 0.7917 g of anhydrous sodium thiosulphate (Na 2 S 2 O 3 ), previously purified and dried in an oven, is weighed into an erlenmeyer flask. This sample is titrated with a mixture of KIO 3 and KI that contains approximately 0.1 M I 3 - . This titration requires 23.56 mL of titrant to reach the endpoint (found

13 2 S20331 S406 ascorbic acid 13 HO dehydroascorbate 31 2H

At 1.00 atm and 0 C, a 5.04 L mixture of methane (CH4) and propane (C3H8) was burned, producing 15.7 g of CO2. What was the mole fraction of each gas in the mixture? Assume complete combustion.

Naphthalene, C 10 H 8 , is the substance present in some moth balls. Its vapor pressure at 25C is 0.300 mm Hg. (a) How many milligrams of naphthalene will sublime into an evacuated 1.000-L flask? (b) If 0.700 mg of naphthalene is used, what will the final pressure be? What physical state(s) of naphthalene is (are) in the flask? (c) If 4.00 mg of

Calculate the heat released as 35.5 g of copper [0.0920 cal/(g C)] cools from 50.0 C to 45.0 C.

Calculate the pH of a buffer solution prepared from 0.155 mol of phosphoric acid, 0.250 moles of KH2PO4, and enough water to make 0.500 L of solution.

Determine the empirical formula of beta carotene knowing that it is 89.49%C and a hydrocarbon.