012 1.0 points Hydrogen chloride in the gaseous state is in the form of covalent molecules, yet in aqueous solution it behaves as a strong electrolyte. The explanation for this solution behavior is that 1. although it is covalent, the molecule of HCl is polar, and stays in solution as a polar molecule, conducting electricity. 2. HCl forms ionic crystals in the solid state. 3. at lower temperatures, HCl becomes ionic. 4. there is more than one form of gaseous HCl. 5. HCl reacts with water to form ions. cor- rect Explanation: The more negative end of the polar water molecule attracts the H end of the HCl. H + is transferred to a water molecule where it is better accommodated due to the greater electronegativity of O. The equation is HCl + H 2 O -→ H 3 O + + Cl − 013 1.0 points Calculate the number of moles of oxygen that will dissolve in 45 L of water at 20 ◦ C if the par- tial pressure of oxygen is 0.21 atm. Henry’s constant for oxygen is 0.0013 mol L · atm . 1. 0.012 mol correct 2. 0.0013 mol 3. 0.00027 mol 4. 0.28 mol
spano velasco (ds28282) – hw 02 – Fakhreddine – (52395) 5 5. 0.0062 mol Explanation: 014 1.0 points Which of the following alcohols would be the least miscible with water? 1. pentanol (CH 3 CH 2 CH 2 CH 2 CH 2 OH) 2. propanol (CH 3 CH 2 CH 2 OH) 3. hexanol (CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 OH) correct Explanation: Water is a polar liquid and for another liquid to be miscible with water it too must be polar. Least miscible means liquid which does not mix with water; i.e. , which is non-polar. Hexanol has the longest non-polar region, so it will be least miscible. 015 1.0 points The formation of tiny bubbles when a beaker of water is mildly heated indicates that 1. air is less soluble in water at higher tem- peratures. correct 2. the liquid is at its boiling point. 3. water is being extensively hydrogen bonded. 4. the lattice energy of water is large. 5. water is being decomposed into hydrogen and oxygen. Explanation: The bubbles are tiny pockets of air that were dissolved in the water at the lower tem- perature. As the gas molecules acquired more energy they were able to escape from the sol- vent. 016 1.0 points Several interesting observations from the world around you are listed below. Which of these is NOT explained by a colligative property? 1. At high altitude it takes longer to cook spaghetti. correct 2. Antifreeze is added to a car radiator to keep the car from overheating. 3. Water boils at a higher temperature when salt is added. 4. A lobster will die when placed in fresh water. 5. The freezing point of water is lowered when salt is added. Explanation: Colligative properties of a solution depend on the number of solute particles in solution, not the type. Boiling point variations due to pressure changes have nothing to do with solutions and colligative properties (boiling point variations due to particles in solution, etc.).
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