CHEM1010 final
It easier to cool off on a dry day vs. a humid day because the rate of evaporation is ________.
greater on a dry day and more heat is lost
Relative to pure water, an aqueous sugar solution ________.
has a lower freezing point because crystal formation is inhibited by the sugar molecules
releases heat
condensation, freezing
A strong acid tends ________.
to be strongly polar to form positively charged ions when dissolved in water to form negatively charged ions when dissolved in water
Starting with the partially balanced equation, CH3COOH(l)+?O2(g)→2CO2(g)+2H2O(l) what coefficient should be placed in front of O2 to balance the oxygen atoms?
2
Starting with the partially balanced equation, CH3COOH(l)+O2(g)→?CO2(g)+2H2O(l) what coefficient should be placed in front of CO2 to balance the carbon atoms?
2
Starting with the unbalanced equation for the combustion of ethanoic acid, CH3COOH(l)+O2(g)→CO2(g)+?H2O(l) what coefficient should be placed in front of H2O to balance the hydrogen atoms? Express your answer numerically as an integer.
2
What set of coefficients is necessary to balance the following chemical equation? ____ Ce4+ + ____ Cl- → ____ Ce3+ + ____ Cl2
2Ce4++2Cl−→2Ce3++Cl2
Which of the following materials is most likely to undergo oxidation?
Cs, Na, K
he formation of hydrogen bonds between water molecules
- Releases heat energy
heat is absorbed by a substance when that substance
- melts - evaporates
It is important to protect water pipes in your home from freezing because ________.
- water expands more than the pipe material, which will fracture the pipes if water in them freezes
Which of the following statements best describe the usual properties of most compounds besides water?
-The density of a material increases when it solidifies. -The volume of a material decreases when it solidifies.
According to the following balanced chemical equation, if you want to generate two moles of H2O, how many moles of O2 do you need? 2 H2 + O2 → 2 H2O
1
Which of the following contains the most heat energy?
1 gram of steam at 100°C
How many electrons are gained or lost in the following half-reaction? Na → Na+ Are electrons gained or lost?
1, lost
Which of the following statements about strong or weak bases are true? Check all that apply.
A strong base will readily accept protons from even weak acids. A strong base completely separates into ions in water. A strong base will react with a strong acid.
Which of the following statements about strong or weak acids is true?
A weak acid will react with a strong base.
what is an endothermic reaction?
All of the above
Which of the following describes an electrode?
Any material that conducts electrons into a media where electrochemical reactions are taking place. OR Any material that conducts electrons out of a media where electrochemical reactions are taking place.
If the following graphs are for the same reaction, which one is most likely the one with an added catalyst?
B, stars in the middle, ends at the bottom
Which of the following species is the reducing agent? 2 CuBr → 2Cu + Br2
Br-
Which of the following species is undergoing oxidation? 2 CuBr → 2Cu + Br2
Br-
Why might disposing of a lead-acid battery, nickel-cadmium battery or mercury battery in a landfill be a bad thing?
Cadmium, mercury, and lead are all toxic metals and could leak out of the landfill.
Sometimes an individual going through a traumatic experience cannot stop hyperventilating. In such a circumstance, it is recommended that the individual breath into a paper bag or cupped hands as a useful way to avoid an increase in blood pH, which can cause the person to pass out. Explain how this works.
Carbon dioxide initially exhaled is reinhaled to help maintain adequate levels of carbonic acid in the blood.
Which of the following species is the oxidizing agent? 2 CuBr → 2Cu + Br2
Cu+
Which of the following species is undergoing reduction? 2 CuBr → 2Cu + Br2
Cu+
Given the following energy profiles, which of the following reactions is endothermic? R= reactants P= products
D (curve starts at the bottom left and ends at the top right)
What is the primary difference between a fuel cell and a battery?
Fuel cells do not run down because they can be refueled; batteries run down and need to be recharged.
According to the following reaction, which molecule is acting as a base? H2O + H2SO4 → H3O+ + HSO4-
H20
According to the following reaction, which molecule is acting as an acid? H2O + NH3 → OH- + NH4 +
H2O
According to the following reaction, which molecule is acting as an acid? H2O + H2SO4 → H3O+ + HSO4 -
H2SO4
What is pH?
It is a numerical scale used to represent acidity or basicity. Also it is the negative of the log of the hydronium ion concentration.
What is a chemical equation?
It is a shorthand notation for illustrating a chemical reaction.
What is the main characteristic of a strong acid?
It is completely dissociated in water.
What is the main characteristic of a strong base?
It is completely dissociated in water.
What is a reaction rate?
It is the speed at which reactants are consumed or product is formed.
Why does soap decrease the surface tension of of water?
It keeps water molecules away from the surface.
For the following acid-base reaction, identify what compound is formed in the space marked. HCl + KOH ↔ ???? + H2O
KCL
For the following acid-base reaction, identify what is formed in the space marked. HF + KOH ↔ ???? + H2O
KF
For the following acid-base reaction, identify what compound is formed in the space marked. HNO3 + KOH ↔ ???? + H2O
KNO3
Which of the following statements about oxidation and reduction reactions is true?
More than one electron can be transferred in an oxidation and reduction reaction.
Why does water have a high specific heat?
Much of the added energy is required to break hydrogen bonds.
Balance the following chemical equation. ____ N2 + ____ H2 → ____ NH3
N2+3H2→2NH3
According to the following reaction, which molecule is acting as a base? H2O + NH3 → OH- + NH4+
NH3
For the following balanced reaction, which of the following is a solid? 2 Na(l) + Cl2(g) → 2 NaCl(s)
NaCl
What is an exothermic reaction?
None of the above
Which of the following statements is(are) not true about a neutralization reaction? Check all that apply.
One molecule of acid neutralizes one molecule of base. Water is always formed in a neutralization reaction. A neutralization is the reaction of a hydroxide ion with a proton.
Which of the following is a correctly balanced equation?
P4 + 6 H2 → 4 PH3
Which of the following statements describes a neutral solution?
[H3O+]/[OH-] = 1
Clorox is a laundry bleaching agent used to remove stains from white clothes. Suggest why the name begins with Clor- and ends with -ox.
The active ingredient contains chlorine atoms, which behave as strong oxidizing agents.
Is the food compartment in a refrigerator cooled by evaporation or condensation of the refrigerating coolant?
The food compartment of a refrigerator is cooled by evaporation of the refrigerating fluid because vaporization is a cooling process.
How does formula mass differ from atomic mass?
The formula mass of a substance is the sum of the atomic masses of the elements is its chemical formula. The atomic mass is the mass of a single atom.
Why might coating a metal with another metal that is harder to oxidize prevent the first metal from being oxidized?
The metal that is coated is protected from moisture and oxygen so it doesn't react.
Why does a paper clip float when placed on water?
The molecules of water hold together and keep it from sinking.
What best describes what happens when an acid such as HCl is mixed with water?
The proton chemically bonded to the chlorine is transferred to a water molecule and forms a chloride ion and a hydronium ion.
Why do water drops bead on a freshly waxed surface?
The strong cohesive forces between water molecules attract each other and the result is a sphere, which is squashed down into a bead by the force of gravity.
What element is oxidized in the following equation and what element is reduced? Sn2+ + 2 Ag → Sn + 2 Ag+
The tin ion, Sn2+, is reduced. The silver, Ag, is oxidized.
Why does water expand when it goes from a liquid to a solid?
The water molecules become aligned in a way that creates extra volume.
Why does sweat cool you off?
The water molecules leaving the skin as vapor absorb the heat from your skin.
The yeast in bread dough feeds on sugar to produce carbon dioxide. Why does the dough rise faster in a warmer area?
There is a greater number of effective collisions among reacting molecules.
A great deal of heat is released when liquid water freezes. Why doesn't this heat simply remelt the ice?
This heat is radiated outwards to the environment, rather than back into the ice.
Why are drops of water shaped like spheres?
Water molecules at the surface are pulled into the liquid, making the drop as small as possible.
Why does blowing over hot soup cool the soup?
When you blow over the top of a bowl of hot soup, the moving air reduces pressure atop the soup and increases the rate of evaporation. When you blow over the top of a bowl of hot soup, you remove the warm vapor which tends to condense and reduce net evaporation above the bowl When you blow over the top of a bowl of hot soup, you increase net evaporation.
Can a glass be filled to above its brim with water without the water spilling over the edge?
Yes, due to the strong cohesive forces between water molecules.
Which of the following statements describes a basic solution?
[H3O+] < [OH-]
Which of the following statements describes an acidic solution?
[H3O+] > [OH-]
Which equations are balanced? a) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g) b) 3Al (s) + 3 Br2 (l) → Al2Br3 (s) c) 2HgO (s) → 2 Hg (l) + O2 (g)
a and c
Electrolysis is an example of ________.
a chemical change
A fuel cell produces electrical energy from ________.
a fuel
The ________ is what needs to be overcome in a reaction so that it can proceed to the products.
activation energy
Which of the following has the greatest number of particles?
all are the same
Which of the following statements best describes an anode?
all of the above
Which of the following statements about catalysts is NOT true?
all of the above are true
Evaporation is ________.
always a cooling process an endothermic process
The specific heat of a substance is the ________.
amount of heat required to change the temperature of a given mass
What is a base?
anything that accepts a hydrogen ion
What is an acid?
anything that donates hydrogen ions
appear before the chemical formulas appear as subscripts of the reactants should always sum up to those of the products Two of the above are correct.
appear before the chemical formulas
Reading the graph from left to right, what phase changes occur? Check all that apply.
boiling
A battery operates by ________.
both oxidation and reduction
Does soap increase or decrease water's surface tension?
decreases
Condensation is ________.
en exothermic process always a warming process
Why is oxygen usually an oxidizing agent?
it is a very electronegative element
absorbs heat
melting, sublimation, evaporation
X + Y → Z Which of the above reactions would proceed the fastest?
most dense, fastest
Acid rain is from dissolved carbon dioxide. All rain is acid rain because rain has a pH is less than 7. Rain is normally basic, but depending on the weather it can get slightly acidic. All rain is acid rain because rain has a hydronium ion concentration greater than 10-7 M. none of the above
none of the above
Which of the following statements best describes a cathode?
none of the above
Which of the following solutions is the most acidic?
ph of 4
The hydroxide ion, HO-, is a ______
polyatomic ion
The hydronium ion, H3O+, is a ________.
polyatomic ion proton donor
Surface tension is the ________.
tendency for molecules at the surface of a liquid to hold together
A chemical equation for the combustion of propane, C3H8, is shown below. Through this reaction is the carbon oxidized or reduced? C3H8 + 5 O2 → 3 CO2 + 4 H2O
the carbon is oxidized
What is reduction?
the gain of electrons
Upon ingestion, grain alcohol, C2H6O, is metabolized into acetaldehyde, C2H4O, which is a toxic substance causing headaches as well as joint pains typical of a "hangover." Is the grain alcohol oxidized or reduced as it transforms into acetaldehyde?
the grain alcohol is oxidized
What is oxidization?
the loss of electrons
What is the activation energy?
the minimum amount of energy to break the bonds in reactants
What is the purpose of the salt bridge in a voltaic cell?
to allow for a balance of charge between the two chambers
What are the formula masses of water, H2O; propene, C3H6; and 2-propanol, C3H8O?
water: 18 amu; propene: 42 amu; 2-propanol: 60 amu
What is a chemical reaction?
when one or more new compounds are formed by rearranging atoms