Chem 112 Exam 1 Version A Questions With 100% Verified Answers

The density of a solution that is 18.0% by mass lead nitrate [Pb(NO3)2] is 1.18 g/cm3. Calculate the molarity of the lead nitrate solution. - correct answers b. 0.64 M What is the definition for molality? - correct answers d. moles of solute/Kg of solvent How many moles of sucrose, C12H22O11, is present in 80.0 grams of an aqueous solution that is 3.50% sucrose by mass? MM(C12H22O11) = 342.30 g/mol - correct answers a. 8.18 x 10^-3 moles At 20 C the Henry's law constant for N2O is 2.72 102 molal/atm. How many grams of N2O (molar mass = 44.0 g/mol) will dissolve in 180 g of water (molar mass = 18.0 g/mol) at 20 C if the pressure of N2O above the solution is 1.5 atm? - correct answers c. 0.32 g The solubility of a substance decreases with increasing temperature: - correct answers b. when the enthalpy of solution is negative The boiling point of pure benzene (C6H6) is 80.10 C. A solution of 7.39 g of a solid dissolved in 85.0 g of benzene boils at 82.49 C. If kb for benzene is 2.53 C/molal, the molar mass of the solid is: - correct answers c. 92.0 g/mol What is the van't Hoff factor, "i", for an aqueous solution of Calcium Nitrate? - correct answers c. i = 3 The equilibrium constant for the reaction below is at 25 °C. 2 HCl (g) H2 (g) + Cl2 (g) Keq(25 C) = 3.2 1034 What can be stated about the relative equilibrium distribution for this mixture? - correct answers c. The mixture contains predominantly HCl. For the reaction 2 C2H2 (g) + 5 O2 (g) 4 CO2 (g) + 2 H2O (g), the expression for Kc is - correct answers e. Kc [CO2 ] 4 [H2O]2 / [C2H2 ] 2 [O2 ] 5 Two (2.00) moles of NO, one (1.00) mole of Cl2, and two (2.00) moles of NOCl are placed in a 1.00 liter flask. If Kc for 2 NO (g) + Cl2 (g) 2 NOCl (g) is 2.72 at this temperature, what occurs in the flask as equilibrium is approached? - correct answers d. The [NOCl] increases. Consider the reaction: PCl3 (g) + Cl2 (g) PCl5 (g) Kc = 4.2 102 A chemist charged a 1.00 liter reaction vessel with 0.125 moles of PCl5, 0.250 moles of Cl2 and 0.375 moles of PCl3. If the equilibrium constant, Kc, for this reaction is 4.2 102, what is the reaction quotient, Qc, and what can be stated about the direction in which this reaction is occurring? - correct answers e. Qc = 1.33 and the reaction is proceeding from right to left as written. The equilibrium constant Kc is 3.00 for NOCl2 (g) NO (g) + Cl2 (g). Initially, 1.33 mol of NOCl2 are placed in a 1.00 liter container. Which of the following is true at equilibrium? - correct answers a. [NOCl2] = 0.33 M For the reaction NH4NO2 (s) N2 (g) + 2 H2O (g), the expression for Kc is - correct answers a. [N2 ][H2O] [NH4NO2 ] What is the molar solubility of PbI2 in 0.25 M NaI? Ksp(PbI2) = 7.9 109 (Hint: Assume "x" is small to make math easier.) - correct answers d. [PbI2] = 1.3 107 M What is the definition for mass percent solute? - correct answers d. (grams of solute / grams of solution) 100% How many grams of AgNO3 are present in 50.0 mL of a 12.0 M AgNO3 solution? MM(AgNO3) = 169.88 g/mol - correct answers c. 102 g of AgNO3 What is the mole fraction of glycerol for a mixture prepared by mixing 300 grams of glycerol (non-volatile solute) and 505 grams of H2O? Molar Mass(glycerol) = 92.09 g/mol and Molar Mass(H2O) = 18.02 g/mol - correct answers a. glycerol = 0.104 What is the molality of a solution prepared by dissolving 76.5 grams of glycine (NH2CH2COOH) in 1.280 kg of water? MM(glycine) = 75.07 g/mol - correct answers b. 0.796 m What is the vapor pressure of water above a solution prepared by adding 15.0 grams of lactose (C12H22O11) to 100.0 grams of water at 338 K? The vapor pressure of pure water at 338 K equals 187.5 torr. Molar Mass(C12H22O11) = 342.30 g/mol and Molar Mass(H2O) = 18.015 g/mol. - correct answers e. 186 torr Given: N2 (g) + 3 H2 (g) 2 NH3 Kc(eq 1) = 2.25 106 What is the equilibrium-constant, Kc, for the formation of one mole of ammonia from nitrogen and hydrogen at 600 K as shown below? 1/2 N2 (g) + 3/2 H2 (g) NH3 Kc(eq 2) = ?? - correct answers c. 1.5 103 Consider the following system at equilibrium and its corresponding concentration equilibrium constant: 3 O2 (g) 2 O3 (g) Kc = 1.8 1056 at 570 K What is the value of Kp for this reaction at 570 K? - correct answers b. Kp = 3.85 1058 For the reaction I2 (g) + Cl2 (g) 2 ICl (g), the relation between Kp and Kc is: - correct answers a. Kp = Kc Consider the following chemical reaction at equilibrium: 2 CH4 (g) + O2 (g) 2 CO (g) + 4 H2 (g) What is the effect of adding more O2 to this system at equilibrium? - correct answers a. The system momentarily proceeds from the left side to the right side until equilibrium is re-established. Some N2H4 is placed in a 1.0 L container, which is sealed, and raised to 1273 K. After the reaction, chemical analysis shows that the concentration of H2 is 0.20 M, N2 is 0.10 M, and N2H4 is 0.10 M. Calculate Kc for: N2H4 N2 + 2 H2 - correct answers a. 0.040 The solubility of CaF2 in water is 3.5 × 10−4 mol/liter. What is the Ksp for this compound? - correct answers d. 1.7 1010