bio 120 ch 2

Which of the following are common features of chemical reactions?

- Chemical reactions proceed toward equilibrium. - Many chemical reactions that occur in cells require catalysts. - Chemical reactions require a source of energy. - Many chemical reactions in living organisms take place in a watery environment. - NOT: Chemical reactions cease when they reach equilibrium. Reason: Chemical reactions do not stop at equilibrium. At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction, so there is no net change in the concentrations of reactants and products.

Within an atom, --- and neutrons have nearly equal masses, while --- have a much smaller mass.

- blank 1: protons - blank 2: electrons

What occurs during all chemical reactions?

Chemical bonds are broken or formed.

True or false: An element is made up of two or more types of atoms.

False, only one type.

What four elements are the most common in living organisms?

Oxygen, Hydrogen, Nitrogen, and Carbon.

A Na+ ion forms when:

a sodium atom loses an electron

The capacity to do work is known as: a)energy, b)kinetic energy, c)chemical energy, or d)potential energy?

a) energy, the other options are just one form of energy

The hydrogen bonds between water molecules form between:

an oxygen atom on one water molecule and a hydrogen atom on a second water molecule (polarity)

Molecules with covalent bonds:

are flexible within certain limits (Covalent bonds are flexible. Molecules can rotate around covalent bonds. Molecules that have covalent bonds have flexible three-dimensional shapes.)

Electronegativity is the ability of an atom to:

attract electrons

What type of compound minimizes pH fluctuations in the fluids of living organisms? a) water, b) buffer, c) acid, or d) base

b) buffer

When two water molecules are near each other, a hydrogen bond will form between the more positive --- and the more negative --- atoms of neighboring water molecules.

blank 1: hydrogen blank 2: oxygen

pH is defined as the --- --- to the base 10 of the --- ion concentration.

blank 1: negative blank 2: logarithm blank 3: H+

An atom's atomic number is based on the number of --- it contains. In an atom that is not in a chemical reaction, the number of protons equals the number of ---.

blank one: protons blank two: electrons

Living organisms minimize changes in their internal pH using compounds called:

buffers

Atoms share a pair of electrons when they form a --- bond.

covalent

If an atom gains or loses a(n) ---, it acquires a net electrical charge and becomes an ion.

electron

An atom or ion is most stable when its outermost shell is occupied by its full complement of ---.

electrons

An atom's atomic number represents:

number of protons

By mass, the most abundant element in living organisms is:

oxygen (hydrogen by number)

The --- of a solution is the negative base 10 logarithm of the H+ concentration of the solution.

pH

Pure water can ionize into:

positively charged protons (H+) and negatively charged hydroxide (OH-) ions.

Which two (sub-atomic) particles are the primary determinants of an element's atomic mass?

protons and neutrons. electrons have negligible mass