CHM 211 Section 210 Test 5: Chemistry Problems and Discussion Questions, Exams of Chemistry

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CHM 211 Section 201 Name:__________________ Test 5: 50 minutes. Please Print Read questions carefully. If you get stuck on a question, move on & come back to it later. If you do not understand a question, ask (earlier the better). If you think you have found a typo, let me know ASAP. Problems 1-10 are multiple choice questions worth 4 points each. Please, write the answer as a CAPITAL letter on the left margin.

1. Which of the following compounds is not planar? A) SO 3 B) XeF 4 C) PF 3 D) H 2 O E) BCl 3 2. Which of the following is a nonpolar molecule: A) O (^) C H ^ H B) O ^ H^ H C) S ^ O^ O D) C C F F^ F F E) N H (^) H H 3. Pressure of 2.75 atm is approximately A) 2.79 Pa B) 2.7910^1 Pa C) 2.7910^3 Pa D) 2.7910^5 Pa E) 2.7910^7 Pa 4. Which of the following is not one of the assumptions of kinetic-molecular theory: A) Total volume of the molecules of gas is negligible in comparison with the volume of the container. B) The attractive forces between molecules are negligible in comparison to kinetic energy of the molecules. C) The collisions between the molecules are perfectly inelastic. D) The molecules are in continuous motion. E) The average kinetic energy of molecules at a given temperature is same for all gases. 5. When volume of container decreases at constant temperature, the pressure inside increases. This is because: A) the volume of each molecule decreases B) the molecules move faster C) the molecules move slower D) the molecules collide with greater momentum with the walls of the container E) none of the above 6. Compared to helium, sulfur dioxide will escape through a pinhole A) 16x slower B) 4x slower C) 2x faster D) 4x faster E) 16x faster

7. Hydrogen bonding does not occur in: A) H 2 O B) CH 3 OH C) HF D) NH 3 E) CH 4 8. Consider following phase diagram: P 1. 2. 3. T The areas marked by numbers 1, 2, and 3 correspond to the following phases: A) solid, liquid, gas B) gas, liquid, solid C) solid, gas, liquid D) liquid, gas, solid 9. What type of solids is characterized by softness, low melting point, poor thermal and electrical conductivity? A) molecular B) covalent network C) ionic D) metallic E) all of the above 10. The volume of helium-filled balloon is 12 L at 10°C and 1 atm. The volume of this balloon at 20°C and 2 atm is approximately A) 3 L B) 6 L C) 12 L D) 24 L E) 48 L Problems 11-16 are discussion questions. Show all of your work ; otherwise you get no credit! Make sure you express the result to the correct number of significant figures. Don’t forget units! If you get stuck on part a), check out the later parts, they are not necessarily dependent! 11. (4 points each = 8 points total) Write balanced equations for reactions that occur in each of the following cases: a) aqueous solution of hydrochloric acid reacts with solid calcium carbonate b) chlorine gas reacts with water

12. (8 points) Sally Scientist is analyzing the amount of KOH in waste stream from manufacture of soap. What is the concentration of KOH in Sally’s sample, if she needed 21.3mL of 0.127M solution of H 2 SO 4 to titrate 100.0mL of the sample? 13. (8 points) Determine molar mass of a vapor that has a density 7.135 g/L at 12°C and 0.945 atm. 14. (12 points) The heat of vaporization of CCl 2 F 2 (which used to be used as a refrigerant) is 289 J/g. What mass of this compound must evaporate in order to cool 100g of water from 18°C to 0°C and freeze it? The heat of fusion of water is 334 J/g; the specific heat of water is 4.18 J/g.K.

15. (12 points) a) What are the mole fractions of each component in a mixture of 3.45 g of O 2 and 5.75g of N 2? b) What is the partial pressure of each component of this mixture if it is held in a 13. L container at 55°C? 16. (12 points) Calcium hydride reacts with water to form hydrogen gas: CaH 2 (s) + 2 H 2 O(l)  Ca(OH) 2 (aq) + 2 H 2 (g) How many grams of CaH 2 are needed to inflate a lifeboat with 375L of hydrogen gas at 10°C and 1 atm pressure?

17. (bonus – 10 points) At atmospheric pressure, water freezes at 0°C and boils at 100°C. Its triple point is at 0.01°C and 4.58 torr; it’s critical point is at 647.6 K and 217.7 atm. Sketch the phase diagram of water (does not have to be to scale) and use it to explain why ice has smaller density than liquid water.