Question

1)

Water has a high boiling point and low freezing point, high self-cohesion, and lower density in the solid phase than in the liquid phase. All these properties can be attributed to ______________.

		the ability of water molecules to hydrogen bond with one another
		repulsion of hydrophobic (nonpolar) solutes by water molecules
		the ability of water molecules to form covalent bonds with one another
		the inability of water molecules to interact with amphipathic solutes

2)

Based on your knowledge of relative electronegativities among the elements common in living cells, which of these chemical groups containing hydrogen would be most likely to participate in forming a hydrogen bond? "R" represents the rest of the molecule.

		R-S–H
		R-C≡C–H
		R-H2C–H
		R-HN–H

3)

In the lining of your stomach, ATP is hydrolyzed to ADP and phosphate ion by a transporter, releasing energy that is used to pump protons (H⁺) from interstitial fluid into the stomach lumen. We learned that energy can make a mass accelerate over a distance. What is the mass and what is the distance in the H⁺ transport system?

		Phosphate ion is the mass and ATP→ADP is the distance
		ATP is the mass and ATP-binding site→ADP-release site is the distance
		H+ is the mass and interstitial fluid→lumen is the distance
		The transporter is the mass and interstitial fluid→transporter is the distance

Answer 1

1. The correct answer is option a - the ability of water molecules to hydrogen bond with one another

Explanation: In water molecule, due to high electronegativity on Oxygen atom, Partial charge is created on Hydrogen atom and in due course this partially positive charged H atom form hydrogen bond with other such molecules. Due to such hydrogen bond formation in Water molecule, it has high boiling point and low freezing point, high self-cohesion, and lower density in the solid phase than in the liquid phase

2. The correct answer is option d - R-HN–H

Explanation: Here C ,S and N are bonded with Hydrogen atom in the four molecules. Carbon has electronegativity value 2.55, Sulphur has electronegativity value 2.6 and Nitrogen has electronegativity value 3.0. So Nitrogen is more electronagative in comparison to C and S. Hence in R-HN–H molecule , more partial positive charge accumulate on the H atom, and hence it will form H-bond more easily.

3.The correct answer is option c -  H⁺ is the mass and interstitial fluid→lumen is the distance

Explanation: H+ ions moves from interstitial fluid to lumen of the stomach as a result of energy liberated by ATP hydrolysis. So the molecule which is transferred is the proton and the distance it covers it from interstitial fluid to the interior of the stomach.