Question
SHOW YOUR WORK VERY, VERY CLEARLY TO GET A FULL MARK. 1. Calculate the gram molecular weight of a volatile liquid. if 0.22 g of it occupies 199 mL at 100 ce and 760 nun Hg. 2. flow much water must be added to 25.0 ml of 0.5 m KOH solution to produce a solution whose concentration is 0.35 M? 3. How many grams of potassium nitrate, KNO3, are needed to prepare 250.0 ml of a 3.00 x 10^-2 M KNO3 solution? 4. In a common freshman laboratory experiment, KCIO3, is decomposed by heating to give KCl and O2. What mass of Keith must be decomposed to give 238 mL 02 at a temperature of 28 ^C and a pressure of 752 torr? (Hint: Balance the equation first) 5. Calculate the molecular mass of a liquid that, when vaporized at 98 degree C and 756 torr give 139 ml, of vapor with a mass of 0.808 g. 6. A bottle of reagent-grade hydrochloric acid has the following information on its label: Assay: 37.0 % HC1 by weight; Density: 1.19 g/mL. (a) Determine the molarity of the acid solution: (b) How many milliliters of the solution are needed to prepare 100 mL o 0.30 M solution by dilution? 7. A 300-mL sample of gas exerts a pressure of 450 tort at 27 degree C. What pressure (in tort) would it exert in a 200-mL container at 20 degree C? 8. Nitric acid is produced by dissolving NO2 in water according to the equation 3NO2(g) + H2O right arrow 2HNO3(l) + NO(g) w many milliliters of NO2 at 25 degree C and 770 torr are required to Produce 10.0 2 of HNO3?
Explanation / Answer
For Question-1.
Let Gram molecular weight=M,
mass given=0.22g, so number of moles=0.22/M
Volume of volatile liquid=199ml = 199*10-3 litre
Temperature=100+273 K=373 K
Pressure=760 mm of Hg=1atm
Applying ideal gas equation for the vapour of this volatile liquid, PV=nRT and putting the values, we get
1atm * 199*10-3 litre = (0.22/M) mol*0.082 litre-atm/mol-K * 373K
M=33.8 g/mol
