Ch 02 HW
The following reaction produces water as one of the products. Choose the correct molecular formula to fill in the blank, making sure to balance the equation. 2(CO2) + 4(H2) => CH3COOH + _______
2(H2O)
This atom can form up to _____ single covalent bond(s).
4 There are four electrons in the outermost electron shell.
Which one of these is an amino group?
A This is an amino group, NH2
Which of the functional groups behaves as a base?
A the electronegativity of nitrogen means that amino groups tend to pick up hydrogen ions
Which statement best explains the energy transformation that occurs when methane reacts with oxygen to produce carbon dioxide and water (CH4 + 2 O2—→ CO2 + 2 H2O)?
A decrease in potential energy from reactants to products is released as heat. The potential energies of the electrons in CO2 and H2O are lower than those of the electrons in CH4 and O2, resulting in the release of heat in this exothermic reaction.
P. americanus produces a small antifreeze protein (AFP) that binds to ice crystals as they form. The structure of AFP has polar groups on one side and nonpolar groups on the other. Propose a hypothesis to explain how AFP prevents cells from freezing solid.
AFP binds to ice crystals and forms a nonpolar shell that prevents *hydrogen bonding* between water molecules to form a larger crystal. By limiting crystal growth, the cell would not freeze solid.
Which of these is a phosphate group?
B Of the choices, this is the only one that contains phosphorus.
Which of these groups plays a major role in energy transfer?
B Phosphate groups are a component of ATP.
Which of these is a carbonyl group?
C
Which of these functional groups is characteristic of alcohol?
D Hydroxyl groups are characteristic of alcohol.
Which of these is a hydroxyl group?
D This is a hydroxyl group.
Which of these groups is characteristic of thiols?
E thiols are characterized by the presence of a sulfhydryl group
Which functional group behaves as an acid?
F By donating hydrogen ions, carboxyl groups act as an acid.
Which of these is a carboxyl group?
F This is a carboxyl group
Which of the bonds is the weakest?
Hydrogen Bonds are weaker than covalent bonds because they do not involve sharing of electrons, and they are weaker than ionic bonds because they involve the attraction of partial (not full) opposite charges.
If water were a linear (not bent) molecule like CO2, electrostatic interactions between water molecules would be much weaker. Why?
In a linear water molecule, the partial positive charges of the two hydrogen atoms would be on either side of the oxygen atom, thus the partial negative charge on oxygen would stick out less and be less able to participate in hydrogen bonding.
Why are covalent bonds between hydrogen and nitrogen or oxygen polar?
Nitrogen and oxygen are more electronegative than hydrogen so electrons are shared unequally.
How does the surface metabolism model of chemical evolution differ from the prebiotic soup model?
Only the surface metabolism model invokes mineral catalysts. Unlike the prebiotic soup model, the surface metabolism model claims that metals may have played an early catalytic role.
Which functional group is least polar? -Hydroxyl -Amino -Carboxyl. -Sulfhydryl
Sulfhydryl The electronegativity of sulfur (S) is only slightly higher than that of hydrogen (H)
If a reaction is exothermic, then which of the following statements is always true?
The products have lower potential energy than the reactants.
If a reaction is exergonic, then which of the following statements is always true?
The reactants have lower potential energy (free energy) than the products.
How does the pH of the solution on the right compare with that of the solution on the left?
The solution on the right is basic relative to the solution on the left. The solution on the right has a lower concentration of hydrogen ions relative to hydroxide ions than does the solution on the left.
What type of bond is joining the two hydrogen atoms?
covalent A covalent bond is one in which electron pairs are shared.
A(n) _____ bond joins these two oxygen atoms.
double covalent The oxygen atoms are sharing two pairs of electrons
The tendency of an atom to pull electrons toward itself is referred to as its _____.
electronegativity
A(n) _____ refers to two or more atoms held together by covalent bonds.
molecule
The unequal sharing of electrons within a water molecule makes the water molecule _____.
polar The electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. Thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.
In this molecule, what type of bond is found between the oxygen and hydrogens?
polar covalent While oxygen shares electrons with hydrogen, the electrons spend more time with the oxygen than with the hydrogens.
