Review Material for Exam #2

Transcription

1 Review Material for Exam #2 1. a. Calculate the molarity of a solution made with mg sample of potassium dichromate dissolved in enough water to give ml of solution. b. What is the molarity of potassium ion? 2. Calculate the mass of sodium hydroxide needed to make ml of a M solution. 3. How would you prepare 1.0 L of 0.50 M sulfuric acid from concentrated (18 M) sulfuric acid? 4. Predict the solubility of each substance in water using solubility rules. Write the ionization reaction when each soluble substance is dissolved in water. a. Ba(NO 3 ) 2 b. ZnS c. (NH 4 ) 2 CO 3 d. Fe 2 O 3 e. PbCl 2 f. NaClO 4 g. BaCrO 4 h. FeBr 2 i. Ag 2 SO 4 j. Ca(OH) 2 k. Hg 2 (ClO 3 ) 2 l. K 3 PO 4 m. Mg 3 (PO 4 ) 2 n. NH 4 NO 3 o. ZnCrO 4 p. NiSO 4 q. AlCl 3 r. AgI s. CaBr 2 t. CuS u. K 2 SO 3

2 5. Predict the products (include phase state), balance and write the net ionic equations for each of the following. Classify each as precipitation, acid-base or oxidation-reduction. Na 3 PO 4 (aq) + AgNO 3 (aq) K 2 SO 4 (aq) + BaCl 2 (aq) Hg 2 (NO 3 ) 2 (aq) + CaCl 2 (aq) Pb(NO 3 ) 2 (aq) + Na 2 SO 4 (aq) AgClO 3 (aq) + KCl(aq) KOH(aq) + H 3 PO 4 (aq) ZnCl 2 (aq) + H 2 S(aq) Na 3 PO 4 (aq) + CaCl 2 (aq) HBr(aq) + Ca(OH) 2 (aq) Na(s) + S(s) C 2 H 6 (g) + O 2 (g) Mg(s) + Cu(NO 3 ) 2 (aq) 6. Determine the oxidation state of each element and identify which element is oxidized and which is reduced. Identify the oxidizing and reducing agents. a. Fe 2 O CO 2 Fe + 3 CO 2 b. PbS + 4 H 2 O 2 PbSO H 2 O c. 8 H 2 O + 3 P HNO 3 12 H 3 PO NO d. 2 MnSO PbO 2 + 3H 2 SO 4 2 HMnO PbSO H 2 O

3 7. If 30.0 ml of M aluminum chloride is added to 15.0 ml of M silver(i) nitrate, what mass of precipitate will be formed? 8. A ml sample of barium hydroxide solution was titrated with ml of M HCl. Calculate the molarity of the barium hydroxide solution. 9. Calcium in blood is determined by precipitating calcium oxalate, CaC 2 O 4, followed by dissolving in acid and titrating the oxalic acid (H 2 C 2 O 4 ) with KMnO 4 : 5 H 2 C 2 O 4 (aq) + 2 MnO 4 (aq) + 6 H + (aq) 10 CO 2 (g) + 2 Mn 2+ (aq) + 8 H 2 O(l) What is the concentration of Ca 2+ (mg/dl) in a 10.0 ml sample of blood if ml of 9.88 x 10 4 M KMnO 4 solution is needed for the titration. 10. Acetylene is a gas used as a fuel for some welding torches. If 0.52 L of acetylene has a pressure of 1824 torr, what is the pressure (in atms) if the volume is decreased to 0.39 L? 11. A sample of carbon dioxide has a volume of 19.4 L at 10.8 C. What is the volume of the same sample of carbon dioxide at 14.6 C. 12. A balloon at 23 C contains 0.32 moles of helium gas at 2432 torr. The volume of the helium is 2.43 L. If an additional 0.14 mole of He is injected into the balloon while holding the temperature and pressure constant, what is the volume of the balloon?

4 13. A sample of Ar has a pressure of 0.63 atm at 26.4 C and a volume of 0.79 L. If the temperature is lowered by 5.2 C and the pressure is increased to 0.96 atm, what is the new volume? 14. Magnesium metal reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas. What mass of Mg reacted with excess hydrochloric acid if 255 ml of hydrogen gas is collected by water displacement at torr and 25.0 o C? See Table 5.2, page Styrene oxide is a fairly simple aromatic organic compound that has a pleasant odor and is often used in the perfume industry. If 2.07 g of the compound is vaporized completely into a closed 1.04 L flask at 435 ºC, the pressure in the flask is found to be 735 torr. Calculate the formula weight of styrene oxide. 16. a. A sample of dichloroethane, a dry cleaning solvent, is vaporized into a ml flask at 99.8 o C. Some of the sample leaves the flask through a pinhole through the stopper until the pressure in the flask is the same as the outside pressure. A barometer shows the pressure to be torr. When the flask is cooled, the mass of dichloroethane in the flask is measured to be g. Calculate the formula weight of dichloroethane. b. Is the formula of dichloroethane CH 2 Cl 2, C 2 H 4 Cl 2, or C 4 H 8 Cl 2?

5 17. Diborane, B 2 H 6, is a highly explosive compound formed by the reaction 3 NaBH 4 (s) + 4 BF 3 (g) 2 B 2 H 6 (g) + 3 NaBF 4 (s) What mass of NaBH 4 is required to give 1.00 L of diborane at 0.0 o C and 1.00 atm? 18. For the reaction, as written: S 8 (s) + 8 O 2 (g) 8 SO 2 (g) H = 2368 kj a. How much heat is evolved when 25 moles of sulfur is burned in excess oxygen? b. How much heat is evolved when 275 grams of sulfur is burned in excess oxygen? c. How much heat is evolved when grams of sulfur dioxide is produced? 19. In a calorimetry experiment, g of Mg ribbon was added to ml M HCl at o C. The water temperature increased to o C. Calculate H for this reaction, as performed, and H per mole of HCl. 20. A 2.50 g sample of sucrose (C 12 H 22 O 11 ) was burned in excess oxygen in a calorimeter which contained 2.19 kg of water. The temperature of the water increased from o C to o C. Determine the molar heat of combustion of sucrose. 21. The burning of 5.08 g benzene (C 6 H 6 ) releases enough heat to raise the temperature of 5.00 kg of water from 10.1 o C to 19.6 o C. Calculate the molar heat of combustion of benzene.

6 22. Given the following equations and H values, H H 3 BO 3 (aq) HBO 2 (aq) + H 2 O(l) 0.02 kj H 2 B 4 O 7 (s) + H 2 O(l) 4 HBO 2 (aq) 11.3 kj H 2 B 4 O 7 (s) 2 B 2 O 3 (s) + H 2 O(l) kj calculate H o rxn for the following reaction: 2 H 3 BO 3 (aq) B 2 O 3 (s) + 3 H 2 O(l) 23. The following reaction is one that occurs in a blast furnace when iron is extracted from its ores: Fe 2 O 3 (s) + 3 CO(g) 2 Fe(s) + 3 CO 2 (g) find H o rxn for this reaction given the following information: H 3 Fe 2 O 3 (s) + CO(g) 2 Fe 3 O 4 (s) + CO 2 (g) 46.4 kj FeO(s) + CO(g) Fe(s) + CO 2 (g) 9.0 kj Fe 3 O 4 (s) + CO(g) 3 FeO(s) + CO 2 (g) 41.0 kj 24. Calculate H o rxn for the following reaction: C 2 H 4 (g) + H 2 (g) C 2 H 6 (g) from the following information: H C 2 H 4 (g) + 3 O 2 (g) 2 CO 2 (g) + 2 H 2 O(l) 1401 kj C 2 H 6 (g) + 7/2 O 2 (g) 2 CO 2 (g) + 3 H 2 O(l) 1550 kj H 2 (g) + 1/2 O 2 (g) H 2 O(l) 286 kj 25. Give the formation reactions for the following compounds: Al 2 O 3, NH 3, N 2 O 5, C 2 H 3 Cl.