ChemH semester 2 exam

which of the following is a factor in the heat capacity of an object

mass

the heat content of a system is equal to the enthalpy only for a system that is at constant

pressure

When 45 g of an alloy, at 25C, are dropped into 100.0 g of water, the alloy absorbs 956 J of heat. If the final temperature of the alloy is 37C, what is its specific heat?

.0423 cal/g°C

the amount of heat released by the complete burning of 1 mole of a substance is its`

heat of combustion

what is the amount of heat required to raise the temperature of 200.0 g of aluminum by 10°C? (specific heat of aluminum = .21 cal/g°C)

420 cal

how can energy change during a chemical reaction

transfer of heat and/or work

what do you know about a chemical reaction if the value of H is postive

the reaction is endothermic

the quantity of heat required to change the temperature of 1 g of a substance by 1 °C is defined as

specific heat

how many kilocalories of heat are required to raise the temperature of 225 g of aluminium from 20 °C to 100 °C (specific heat of aluminum = .21 cal/g°C

3.8 kcal

by definitions which of the following is true of H soln?

it can be positive or negative

what does the symbol H stand for

the heat of reaction for a chemical reaction

which of the following substances has the highest specific heat

liquid water, mercury, ice, steel

liquid water

how much water at 100°C could be vaporized by the addition of 120 kJ of heat? (H vap = 40.7 kJ/mol)

53 g

by what quantity must the heat capacity of an object be divided to obtain the specific heat of that material

its mass

which of the following electromagnetic waves have the highest frequencies

microwaves
gamma rays
x-rays
ultraviolet light waves

gamma rays

which of the following quantum leaps would be associated with the greatest energy of emitted light

n=5 to n=1

what is the maximum number of f orbitals in any single energy level in an atom

7

how does atomic radius change from top to bottom in a group in the periodic table

it tends to increase

the quantum mechanical model of the atom...

involves the probability of finding an electron in a certain position

the light given off by an electric discharge through sodium vapor is

an emission spectrum

what is the approximate energy of a photon having a frequency of 4x10^7 Hz? (h=6.6x10^-34 J*s)

3 x 10 ^-26 J

when an electron moves from a lower to a higher energy level, the electron

absorbs a quantum of energy

how does the energy of an electron change when the electron moves closer to the nucleus

it decreases

what are quanta of light called

photons

Which subatomic particle plays the greatest part in determining the properties of an element?

electron

how does the speed of visible light compare with the speed of gamma rays, when both speeds are measured in a vacuum

the speeds are the same

how are frequency and wavelength of light related

They are inversely proportional to each other

which of the following statements correctly compares the relative size of an ion to its neutral atom

the radius of an anion is greater than the radius of its neutral atom

of the elements P, V, Li, and Kr, which is a nonmetal

Kr

compared to the electronegativities of the elements on the left side of the periodic table, the electronegativities of the elements on the right side of the same period tend to be

higher

each period in the periodic table corresponds to a(n)

principle energy level

how does atomic radius change from left to right across a period in the periodic table

it tends to decrease

which of the following elements is in the same period as phosphorus

oxygen
carbon
magnesium
nitrogen

magnesium

the modern periodic table is arranged in order of increasing atomic...

number

what is the energy required to remove an electron from an atom in the gaseous state called

ionization energy

What element has the electron configuration 1s2 2s2 2p6 3s2 3p2?

silicon

which of the following is true about the electron configurations of the representative elements

the highest occupied s and p sublevels are partially filled

which of the following covalent bonds is most polar

H-F
H-H
H-C
H-N

H-F

experimental evidence suggests that the H-C-H bond angles in ethene, C2H4, are

120°

which of the following diatomic molecules is joined by a double covalent bond
O2
He2
Cl2
N2

O2

What causes water molecules to have a bent shape, according to VSEPR theory?

repulsive forces between unshared pairs of electrons

how does calcium obey the octet rule when reacting to form compounds

it gives up electrons

which of the following theories provides information concerning both molecular shape and molecular bonding

orbital hybridization theory

a resonance structure represents

a hybrid of the extremes represented by the resonance forms

which of the following is the octet expanded to include 12 electrons

SF6

the side-by-side overlap of p orbitals produces what kind of bond

pi bond

which of the following bond types is normally the weakest

pi bond formed by the overlap of two p orbitals

the octet rule states that, in chemical compounds, atoms tend to have...

the electron configuration of a noble gas

which molecule has a single covalent bond

Cl2

the shape of the methane molecule is ...

tetrahedral

According to VSEPR theory, molecules adjust their shapes to keep which of the following as far apart as possible?

pairs of valence electrons

under what conditions of temperature and pressure is the behavior of real gases most like that of ideal gases

high temperature and low pressure

as the temperature of a fixed volume of gas increases, the pressure will

increase

if a balloon is heated, what happens to the volume of the air in the balloon if the pressure is constant

It increases

when the pressure and number of particles of a gas are constant, which is also constant

the ratio of the volume and temperature in kelvins

If 4 moles of gas are added to a container that already holds 1 mole of gas, how will the pressure change inside the container?

the pressure will be five times higher

A gas occupies a volume of 2.4 L at 14.1 kPa. What volume will the gas occupy at 84.6 kPa?

0.40 L

if a sealed syringe in plunged into cold water, in which direction will the syringe piston slide?

in

why does the pressure inside a container of gas increase if more gas is added to the container

there is an increase in the number of collisions between particles and the walls of the container

when the kelvin temperature of an enclosed gas doubles, the particles of the gas

move faster

which of these changes would cause a decrease in the pressure of a contained gas

the volume of the container is increased

which law can be used to calculate the number of moles of a contained gas

ideal gas law

If the atmospheric pressure on Mt. Everest is one-third the atmospheric pressure at sea level, the partial pressure of oxygen on Everest is

one-third its pressure at sea level

A breathing mixture used by deep-sea divers contains helium, oxygen, and carbon dioxide. What is the partial pressure of oxygen at 101.4 kPa if PHe = 82.5 kPa and PCO₂ = 0.4 kPa?

18.5 kPa

If the volume of a container of gas is reduced, what will happen to the pressure inside the container?

the pressure will increase

as the temperature of the gas in a balloon decreases, which of the following occurs

the average kinetic energy of the gas decreases

A sample of gas occupies 17 mL at -112°C. assuming the pressure is held constant, what volume does the sample occupy at 70°C?

36mL

when the volume and number of particles of a gas are constant, which of the following is also constant

the ratio of the pressure and temperature in kelvins

When a container is filled with 3.00 moles of H2, 2.00 moles of O2, and 1.00 mole of N2, the pressure in the container is 768 kPa. What is the partial pressure of O2?

256 kPa

The volume of a gas is doubled while the temperature is held constant. How does the gas pressure change?

it is reduced by one half

what happens to the temperature of a gas when it is compressed

the temperature increases

the products of self-ionization of water are

OH- and H3O+

what is transferred between a conjugate acid-base pair

a proton

which combination of acid and salt in aqueous solution would form a buffer

carbonic acid and sodium carbonate

what is the process of adding a known amount of a solution of known concentration to determine the concentration of another solution called

titration

when an acid reacts with a base, what compounds are formed

a salt and water

what are the bronsted-lowry acids in the following equilibrium reaction

CN- + H2O ---> HCN + OH-

H2O, HCN

which compound can act as both a bronsted lowry and and a bronsted lowry base

water

a lewis acid is a substance that can

accept a pair of electrons

a substance with a Ka of 1x10^-5 would be classified as a

weak acid

in a neutral solution, [H+] is

equal to [OH-]

what is the formula for phosphoric acid

H3PO4

which pH value could represent the equivalence point of the titration of a strong base and a weak acid

pH 9

what is the best description for a solution with a hydroxide-ion concentration equal to 1 x 10 ^-4 M?

basic

why would you use more than one indicator to determine the pH of a solution

indicators generally change color over narrow ranges of pH

which base has the smallest base dissociation constant

ammonia

what is the charge on the hydronium ion

1+

How much H3PO4 is needed to neutralize 1 liter of a 0.75M solution of NaOH ?

0.25 mol

in reference to solutions of strong acids and strong bases, the word strong refers to

degree of ionization

which phrase best describes a 0.012 M solution of an acid that ionizes only slightly in water

dilute and weak

which of the following pairs of compounds consists of a weak acid and a strong base

acetic acid, sodium hydroxide

what is an acid according to the arrhenius definition

a substance that ionizes to yield protons in aqueous solution

the ionization constant (Ka) of HF is 6.7x10 ^-4. which of the following is true in a 0.1 M solution of this acid

[HF] is greater than [H+][F-]

which of the solutions is most basic

[H+] = 1x10^-11 M

which of the following represents a bronsted lowry conjugate acid-base pair

NH4+ and NH3

which of these compounds or ions is an arrhenius base

CH3COO-
LiOH
H2PO4-
NH3

LiOH

how does an indicator provide information about the pH of a solution

by dissociating into ions that have a different color than the molecular form

the formula of the hydrogen ion is often written as

H+

a base has a Kb of 2.5 x 10 ^-11. which of the following statements is true

this base ionizes slightly in aqueous solution

in a titration, shat happens when the number of moles of hydrogen ions equals the number of moles of hydroxide ions

the equivalence point has been reached OR the point of neutralization has been reached