This work was created by Dr Jamie Love and licensed under a Creative Commons Attribution-ShareAlike 4.0 International License Creative Commons Licence.

FIRE
Self Evaluation Test

Welcome to your last Element Exam. (But don't forget to take the Final Exam so you can get your Diploma!) Choose the best answer by selecting one of the buttons.
When you choose an answer you will get a "pop-up" response indicating whether you got it right or wrong. I suggest that the first time you take the test, you simply stick with your original answers, complete the test and submit it for a grade. This will give you an idea of what you have learned so far and is more like a "regular" test (whatever that is). Your answers will be graded and each one will be scored Correct or Wrong. Once you have the score and the list of incorrect answers you can use your "Back Button" to return to your exam and correct your errors. This time, this second time, you can carefully read each response, learn from it and choose the right answer. Students receiving a perfect score will be awarded a Certificate of Completion.
Important note : on some browsers (like some Internet Explorers) when you use the page down button to scroll down you will end up shifting your checked answer to the next one down the line! If that happens to you, use your mouse to scroll - not the keyboard.


FIRE 1 : A chemical reaction that gives off heat is said to be ...

exergonic.
endergonic.
exothermic.
endothermic.

FIRE 2 : Copper slowly oxidizes in a reaction that looks like this
2Cu + O2 ------> 2CuO
and is an example of a _________ reaction.

combination
combustion
corruption
All the above describe the reaction.

FIRE 3 : Hydrogen peroxide breaks down into simple oxygen and water like this
2H2O2 ------> O2 + 2H2O
and is an example of a _________ reaction.

replacement
combustion
decomposition
All the above describe the reaction.

FIRE 4 : Copper reacts with sulfuric acid to make copper sulfate in a reaction like this
Cu + H2SO4 ------> CuSO4 + H2
and is an example of a _________ reaction.

replacement
rust
combustion
All the above describe the reaction.

FIRE 5 : The chemical reaction we call "fire" is ...

a chain reaction.
exothermic.
exergonic.
All the above describe the reaction.

FIRE 6 : An atom or molecule that is oxidized ...

loses an electron.
often gains an oxygen.
increases its valence number (becomes more positive).
All the above are true of oxidation.

FIRE 7 : Solid magnesium (Mg(s)) combines with oxygen gas (O2(g)) to produce a solid called magnesium oxide (MgO(s)). The half reaction for magnesium in this reaction must be ...

[Important hint : magnesium is a Group II element. Think about how that will affect its behavior.]
Mg ------> Mg+1 + e-
Mg ------> Mg+2 + 2e-
1/2 Mg ------> 1/2 Mg + e-
None of the above are the half reaction for magnesium’s oxidation to oxide of magnesium.

FIRE 8 : Continue thinking about the reaction in question 7 and tell me the half reaction for the oxygen.

O + e- ------> O-
O2 + e- ------> O2-
O2 + 2e- ------> 2O-
O2 + 4e- ------> 2O-2

FIRE 9 : Regarding the two half reactions you worked on in questions 7 and 8, magnesium is _________ and oxygen is _________.

reduced, oxidized
oxidized, reduced
reduced, reduced
oxidized, oxidized

FIRE 10 : Use what you have learned in the last few questions to choose a balanced equation that shows how solid magnesium combines with oxygen gas to produce a solid magnesium oxide.

Mg(s) + O2(g) ------> 2MgO(s)
2Mg(s) + O2(g) ------> MgO2(s)
Mg(s) + O(g) ------> MgO(s)
2Mg(s) + O2(g) ------> 2MgO(s)

Sulfur (S) tarnishes sliver (Ag) leaving a nasty looking material made of sliver and sulfur (AgS). Tarnished silverware can be "saved" by boiling it in water in an aluminum pot. (This reaction also needs a pinch of baking soda to help, but we will ignore that here.) The aluminum is important because it takes part in the reaction. The water must be considered too because it provides hydrogens to the products. The unbalanced and partial equation is
AgS + Al ------> Al(OH)3 + H2S + Ag
(I haven't bothered writing in the states of each material because it isn't important here. So don't worry about them in your answer either.)

FIRE 11:This (AgS + Al ------> Al(OH)3 + H2S + Ag) is only a partial equation. What is missing?

Water (H2O).
Oxygen (O2).
Hydrogen (H2).
Nothing. All the elements are accounted for.

FIRE 12 : Here is that unbalanced, but now complete, equation.
AgS + Al + H2O ------> Al(OH)3 + H2S + Ag.
Use it to tell me which atoms do NOT change their valency.

Silver (Ag).
Aluminum (Al).
Sulfur (S), oxygen (O) and hydrogen (H).
None of them. All the atoms change their valency.

FIRE 13 : What is the balanced half equation for silver (Ag) in this unbalanced (but complete) equation?
AgS + Al + H2O ------> Al(OH)3 + H2S + Ag

Ag+1 + e- ------> Ag
Ag+2 + 2e- ------> Ag
Ag+2 + 2e- ------> H+1
Ag+2 ------> Ag + 2e-

FIRE 14: What is the balanced half equation for aluminum (Al) in this unbalanced (but complete) equation?
AgS + Al + H2O ------> Al(OH)3 + H2S + Ag

Al ------> Al+3 + 3e-
Al ------> Al+3 + e-
Al ------> Al+1 + 3e-
Al+3 ------> Al+3 + 3e-

FIRE 15 : OK, now that you have the pair of half equations, use that information to choose the correct balanced equation.

This is not easy so take your time and think how you can work with 3 electrons from Al and 2 electrons from Ag.
3AgS + Al + 6H2O ------> Al(OH)3 + 3H2S + 3Ag
3AgS + 2Al + 6H2O ------> 2Al(OH)3 + 3H2S +3Ag
AgS + 2Al + 6H2O ------> 2Al(OH)3 + H2S + Ag
3AgS + 2Al + H2O ------> 2Al(OH)3 + 3H2S + 3Ag

FIRE 16 : Elements that have multiple valence numbers, such as iron (Fe), are given different endings. The lower valence atom ends in "____" and the higher valence atom ends in "___".

low, hi
mono, di
ic, ous
ous, ic

FIRE 17 : Chemical reactions can often be made to go faster by ...

mixing the reagents together as completely as possible (especially if they are solids).
increase the pressure (especially if the reagents are gases).
increase the temperature (if the reagents and products can stand it).
All the above could make the reaction faster.

FIRE 18 : A catalyst increases the rate of a chemical reaction by ...

lowering the Gibbs energy.
shifting the equilibrium to the right in the equation.
increasing entropy.
creating a special activation complex with a lower transition state.

FIRE 19 : Enthalpy is ...

the amount of disorder in a system.
the energy stored in a compound.
the heat given off in a reaction.
is the total amount of chemical energy in a system.

FIRE 20 : Chemical reactions always run from _________ Gibbs energy to ________ Gibbs energy.

same, different
strongest, weakest
highest, lowest
lowest, highest


You can now submit your exam to Merlin for grading. If your answers were less than perfect you will receive a score and a list of Incorrect (and Correct) replies. Then you can use your "Back Button" to return to this page and correct your earlier errors. Once you have corrected all your earlier errors (by rechoosing a correct answer when you were told you are wrong), you will get a perfect score.


This work was created by Dr Jamie Love and licensed under a Creative Commons Attribution-ShareAlike 4.0 International License Creative Commons Licence.