Chapter 3 Flashcards
in a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by
polar covalent bonds
the slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. what is this attraction called?
a hydrogen bond
the partial negative charge in a molecule of water occurs because
the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus then around the hydrogen atom nucleus
sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon. Compared to water molecules, molecules of H2S
will not form hydrogen bonds with each other
water molecules are able to form hydrogen bonds with
compounds that have polar covalent bonds
Which of the following effects is produced by the high surface tension of water?
a water strider can walk across the surface of a small pond
Which of the following takes place as an ice cube cools a drink?
kinetic energy in the drink decreases
A dietary calorie equals 1 kilocalorie. Which of the following statements correctly defines 1 kilocalorie?
1000 calories, or the amount of heat required to raise the temperature of 1 kg of water by 1 degree C
The nutritional information on a cereal box shows that one serving of a dry cereal has 200 kilocalories. If one were to burn one serving of the cereal, the amount of heat given off would be sufficient to raise the temperature of 20 kg of water by how many degrees C?
10 degrees C
Liquid water’s high specific heat is mainly a consequence of the
absorption and release of heat when hydrogen bonds break and form
Which type of bond must be broken for water to vaporize?
hydrogen bonds
Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?
the release of heat by the formation of hydrogen bonds
Why does evaporation of water from a surface cause cooling of the surface?
the water molecules with the most heat energy evaporate more readily
Why does ice float in liquid water?
hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water
Hydrophobic substances such as vegetable oil are
nonpolar substances that repel water molecules
One mole (mol) of glucose (molecular mass= 180 daltons) is
both 180 grams of glucose and 6.02 x10^23 molecules of glucose
How many molecules of glucose (C6H12O6 molecular mass= 180 daltons) would be present in 90 grams of glucose?
(90/180) x 6.02x10^23
How many molecules of glycerol (C3H6O3; a molecular mass=92) would be present in 1 L of a 1 M glycerol solution?
6.02x10^23
When an ionic compound such as sodium chloride (NaCl) is placed in water, the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-) In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of solute particles (molecules or ions)?
1 L of 1.0 M NaCl
The molar mass of glucose is 180 g/mol. Which of the following procedures should you carry out to make a 1 M solution of glucose?
dissolve 180 g of glucose in 0.8 L of water, and then add more water until the total volume of the solution is 1 L
The molar mass of glucose (C6H12O6) is 180 g/mol. Which of the following procedures should you carry out to make a 0.5 M solution of glucose?
dissolve 90 g of glucose in a small volume of water, and then add more water until the total volume of the solution is 1 L
You have a freshly prepared 0.1 M solution of glucose in water. Each liter of this solution contains how many glucose molecules?
6.02x10^22
The molecular weight of water is 18 daltons. What is the molarity of 1 liter of pure water? (Hint: what is the mass of 1 liter of pure water?)
55.6 M
You have a freshly prepared 1 M solution of glucose in water. You carefully pour out a 100 mL sample of that solution. How many glucose molecules are included in that 100 mL sample?
6.02x10^22