Mastering Bio Ch.3
A buffer consists of undissociated acid (HA) and the ion made by dissociating the acid (A-). How does this system buffer a solution against decreases in pH?
-A reacts with H+ to become HA.-A reacts with H+ to become HA.
If the molecular mass of a carbon atom is 12, the mass of a hydrogen atom is 1, and the mass of an oxygen atom is 16 daltons, how many molecules does one mole of table sugar (sucrose; C12H22O11) contain?
6.02 x 10^23
Select the statement that best describes a buffer.
A buffer resists change in pH by accepting hydrogen ions when acids are added to the solution and donating hydrogen ions when bases are added.
Which answer helps to explain why all living cells need pH buffers?
Amino acid side chains have many carboxyl and amino groups.
Water molecules have a polarity, which allows them to be electrically attracted to other water molecules and other polar molecules by weak chemical bonds known as _____.
Hydrogen bonds
What is the arrow pointing to? (+ single)
Hydrogen ion
What is the arrow pointing to? (- double)
Hydroxide ion
How does the way a buffer stabilizes pH during addition of acid differ from the way the same buffer stabilizes pH during addition of base?
It's the same reaction running backward or forward.
How does the pH of the solution on the right compare with that of the solution on the left? (more single on left)
The solution on the right is basic relative to the solution on the left.
Which statement is true of pH buffers?
They consist of weak acids and weak bases.
All of the following statements help to explain why water molecules form hydrogen bonds except:
Water is an electronegative molecule.
Buffers work best when ...
about half of the buffer molecules are dissociated.
Many of water's emergent properties, such as its cohesion, its high specific heat, and its high heat of vaporization, result from the fact that water molecules _____.
are attracted to each other by partial negative and positive charges on the oxygen and hydrogen atoms, respectively
To make a buffer, you need to ...
have a weak acid or a weak base half ionized in water
Because organisms are made primarily of water, they resist rapid temperature changes. This useful quality is based on water's _____.
high specific heat
In a neutral solution the concentration of _____.
hydrogen ions is equal to the concentration of hydroxide ions
A polar covalent bond between two atoms results from
two atoms that do not have similar electronegativities
Which of the following is a hydrophobic material?
wax
