Exam 2: The Nature of Moleculars and the Properties of Water

Salt is often used to melt ice on roads during the winter because it lowers the freezing/melting point of water. When salt dissolves in water, individual Na⁺ and Cl^- ions break away from the salt lattice and become surrounded by water molecules. Why would this cause ice to melt?

You identify an enzyme involved in a cellular reaction. How does the enzyme affect the reaction equilibrium between reactants and products and the time needed to reach equilibrium?

The half-life of Carbon-14 is approximately 5,700 years. Using this information scientists have been able to determine the age of some artifacts left by humans. A scientist wants to know approximately how old a piece of wood was that she found on the floor in an old cave that had recently been discovered. She removed the wood (with permission) to her laboratory. Her wood sample contained 2 grams of Carbon-14. If the age of the wood was determined to be 22,800 years old, how much Carbon-14 originally existed in this piece of wood?

As you and a friend are entering a chemistry laboratory at your university, you see a sign that states: DANGER-RADIOACTIVE ISOTOPES IN USE. Your friend is an accounting major and has not had any science courses yet. She asks you what a radioactive isotope is and you respond correctly with:

An oxygen atom in water has two covalent bonds with hydrogen atoms and two unpaired electrons. How many hydrogen bonds can a water molecule form?

Which chemical group forms hydrogen bonds with water and is most likely to explain why sugars dissolve well in water?

Cl has 7 electrons in its outer shell and K has 1 electron in its outer shell. How is the bond in Cl₂ different from the bond in KCl?

The electronic configuration of the noble gas Neon, which has an atomic number of 10, can be written as follows: 1s²2s²2p⁶. What is the electronic configuration of the noble gas Argon, which has an atomic number of 18?

Water is most dense and thus heaviest at 4^oC. At 0^oC, ice forms and can float on liquid water. Suppose ice were most dense at 0^oC. What would happen in a lake?

Your dog becomes ill and you rush him to the veterinarian's office. A technician draws blood from your dog's leg for a vet-ordered lab test. After a few minutes the lab results are given to the vet, who immediately grabs a bottle from a shelf and begins to fill a syringe with an unknown fluid. You inquire about the fluid, and the vet informs you that the fluid is necessary to manage your dog's metabolic acidosis. Based on the information provided, what is acidosis, and what is the likely effect of the veterinarian's injection? Acidosis means that your dog's blood pH has ______ from its normal level, and an injection of _____ is required to reverse the condition.

According to most car mechanics, plain water is the best coolant to use in an engine provided the engine is not being exposed to freezing temperatures. If the car is subject to freezing temperatures then a mixture of water and ethylene glycol (antifreeze) is recommended but it does not cool as efficiently as plain water. Why would ethylene glycol reduce the cooling efficiency of water?

The common basilisk lizard will run across water on its hind legs in an erect position when startled by predators. This lizard has large feet and flaps of skin along its toes. What properties of water allow this lizard to walk on water?

Capillary action is one of the forces that aids water's upward movement in plants. The narrower the diameter of the tube, the farther the water column will rise. Capillary action is a result of water molecules:

Membrane lipids contain long chains of H-C-H groups joined by C-C bonds. Which interaction is most likely occurring between lipids in the membrane?

Sulfur is found directly below Oxygen on the periodic table. What type of bond would you predict S-H would form?