[magnaflux]

So for before my grade 11 final exam the teacher gave us an exam review with all the answers for us to study, now I'm normally not one to look at this stuff, but since I believe I'm at about 45% in chemistry I figure I should really study and would just like you guys to assure me or correct me on this stuff.  I might use the wrong terms as I don't really understand this stuff all that great (probably why I'm failing) but most of this stuff should be fairly simple for some of you guys.  Anyways, here goes. If my reasoning is right can you guys just be like "1. Correct" or "1. Wrong" and then explain it properly for me?  Thanks in advance! Bolded will be the question, underlined will be the reason why it's whatever answer it is, italicized will be information for questions following.

*skip 1*

2. A non-electrolyte can be defined as a solute which...
D. dissolved to form a non-conducting solution.

The reason it's D is because I'm pretty sure if a solute is conductive it's called an electrolyte, so it's only logical a non-electrolyte is the opposite.  Am I correct?

Use the following information to answer the next question.
1. Mg(OH)_2(s) --> Mg²⁺_(aq) + 2 OH^-_(aq)
2. HCl_(g) --> H⁺_(aq) + Cl⁺_(aq)
3. CO_2(g) --> CO_2(aq)
4. Fe_(s) --> Fe_(s)

3. A solute dissolving to form a solution is shown by...
D. 1, 2, and 3 only

The reason it's D is because when a solute is dissolved it's state will turn aqueous (spelling?). Am I correct? (if there's another way to figure it out without the states being given can you guys help me?)

Use the following information to answer the next four questions
Solution 1: red litmus, high conductivity
Solution 2: no change in litmus, no conductivity
Solution 3: blue litmus, high conductivity
Solution 4: no change in litmus, high conductivity

4. The solution listed in the table that demonstrates acidic properties is..
a. 1

The answer is a because for the litmus test it turned red which only happens to acidic solutions.  Am I correct?

5. Which solutions listed in the table contain solutes that are ionic compounds?
d. 1, 3, and 4 only.

The answer is d because because ionic compounds have high conductivity.  Am I correct?

6. The solution listed in the table which contains OH^-_(aq) ions is.
c. 3

The answer is c because the Litmus is blue and hydroxide is a very basic compound. I have a feeling I'm way out of the ballpark on this one and I don't really know why c would contain hydroxide, I thought hydroxide was extremely acidic?

*skip 7*

8. According to Arrhenius theory, what happens when the solutes HCl_(g) and NaBr_(s) are dissolved together in distilled water?
d. HCl_(g) would ionize and NaBr_(s) would dissociate

I'm sorry, I just don't understand this at all.. this is one of them I just completely don't get

9. Acids are unique molecular compounds because they
b. form ions in solution

Why is this? I'm sorry.. I try to find the answers but I just can't concentrate, I've already taken an hour and a half just to get to the 9th question.  I'll probably need a lot more explainations in the follow questions.

10. The reaction Ba(OH)_2(aq) --> Ba²⁺_(aq) + 2 OH^- represents the
a. dissociation of a base

Um.. I don't know, again.

Use the following information to answer the next question.
A sample solution is throught to contain one or more of the following ions: Hg₂²⁺, Ba²⁺, Mn²⁺.  No precipitate formed when a solution of NaCl_(aq) or Na₂SO_4(aq) was added to the sample.  A precipitate did form when the sample was made basic by the addition of NaOH_(aq).

11. Which ion was present in the sample solution?
c. Mn²⁺

*sigh* again, I have no clue.. and this is just the basics I believe.


I have to go right now I'll be on again the next few days.. I mean I can't just sit in the same place for 2 hours doing nothing but typing stuff I don't even understand.. but hopefully you guys can help me.. I have a LOT more questions that I'll add on later tonight when I'm rejuvinated.. if this is going to be against any of the forum rules please don't delete it right away so I can atleast copy what I've written out.

[Yggdrasil]

2.  Correct
3.  Correct.  Looking at the states is fine, although it is important to also notice that the ionic compounds dissociate upon dissolving in water.
4.  Correct.
5.  Correct.
6.  Correct.  Solutions that contain high concentrations of hydroxide ions are basic.  Although your answer is correct, the question is bad.  All aqueous solutions will contain some hydroxide ions because water spontaneously dissociates to form a small amount of H⁺ and OH^-.
8.  Although what you say is true, your response doesn't sufficiently answer the question.  Arrhenius theory talks about the definition of acids and bases.  Would the solution be acidic, basic, or neutral?
9.  To answer this question, it would be useful to review the Arrhenius definition of acids and bases in your chemistry textbook or on wikipedia (http://en.wikipedia.org/wiki/Arrhenius_theory#Arrhenius_definition), which is the simplest definition of acid and bases.  Briefly, Arrhenius theory states that acids release H⁺ into solution upon dissolving, and bases release OH^- into solution upon dissolving.
10.  Correct.  The equation represents the dissolution of a base because it results in the formation of OH^- ions.
11.    Certain combinations of ions form insoluble salts.  For example, silver ions will precipitate from solution in the presence of chloride ions because the resulting AgCl salt is insoluble in water.  Therefore, if you adding NaCl and see no precipitate form, you know that no silver ions are present in solution (or else you would see a precipitate).  Conversely, the formation of a precipitate would suggest the presence of silver ions (although the precipitate could be due to the formation of other insoluble salts, so the formation of a precipitate won't absolutely prove that you have silver ions).  So, to answer this question, I'd suggest looking up the solubility of the cations listed in your chemistry text book (unfortunately, I don't remember these off the top of my head, so I can't comment on whether your answer is correct or not.  Perhaps someone else can answer).

[magnaflux]

how can I tell whether the solution will be acidic or basic? I mean I can get it if say it's SO₃^2- + H₂O --> HSO₃ + OH^- because SO₃ obviously can't give a hydrogen ion, but other wise how can you tell?

Also, a big thing I didn't understand in this course was the whole conversion, I have several formulas and I don't know what most the symbols mean, but anyways.  I hope it's not asking too much if I can ask what each formula is used for.

n = m/M
C₁V₁=C₂V₂
P₁V₁=P₂V₂
C=n/V
PV=nRT
P_total= *sigma with an i underneath it* P_i
V₁/T₁=V₂/T₂
P₁/T₁=P₂/T₂
P₁V₁/T₁=P₂V₂/T₂
pH = -log[H⁺_(aq)]
pOH = -log[OH^-_(aq)]
Q = mc*delta*T
*delta*H = nH

and excuse me if this makes sense, there's a few symbols I don't know how to type in this final equation

*delta*H = *sigma* nH^*degree*_f[P] - *sigma* nH^*degree*_f[R]

Also, there's a few of these I don't even know what they mean

n = moles?
m = density?
M = mass?
C = concentration?
R = ??
*sigma* = ??
Q = ?
c = ?
*delta* = difference in pH?
H = ?
[P] & [R] = ?

[vhpk]

how can I tell whether the solution will be acidic or basic? I mean I can get it if say it's SO32- + H2O --> HSO3 + OH- because SO3 obviously can't give a hydrogen ion, but other wise how can you tell?

The easiest method ( in my opinion), you should notice the conjugated part of each anion or cation:
- If the acid is weak ( like acetic acid or sulphurous acid), the solution containing anion is basic, the same with weak base ( like aluminium hydroxide or ferric hydroxide)
- If the acid is strong(like hydrochloric acid or sulphuric acid), the solution containing anion is nearly neutral.
But to guarantee, you should find Ka and Kb before calculating the pH of a solution

[Yggdrasil]

how can I tell whether the solution will be acidic or basic? I mean I can get it if say it's SO₃^2- + H₂O --> HSO₃ + OH^- because SO₃ obviously can't give a hydrogen ion, but other wise how can you tell?

In general, things that have the formula HX, where X is an anion, will be acids.  Examples include HCl, HBr, H₂SO₄, HNO₃.  Organic acids are harder to identify but will often have a -COOH group (e.g. CH₃CH₂COOH).

In general, bases will have the formula AOH where A is a cation.  Examples include NaOH, KOH, etc.  Organic bases are hard to identify without knowing them, but often have a nitrogen (e.g. NH₃, N(CH₃)₃).  Bases can also be recognized as the conjugate bases of weak acids.  For example, HSO₄^- is a weak acid, so its conjugate base, SO₄^2- is a weak base.  Note that H₂SO₄ is a strong acid, so its conjugate base, HSO₄^- is not a base.

n = m/M
C₁V₁=C₂V₂
C=n/V

n = moles
m = mass
M = molar mass
C = concentration
V = volume
P = pressure

The next couple equations deal with ideal gasses

PV=nRT
P₁V₁ = P₂V₂
P_total= *sigma with an i underneath it* P_i
V₁/T₁=V₂/T₂
P₁/T₁=P₂/T₂
P₁V₁/T₁=P₂V₂/T₂

P = pressure
V = volume
n = moles
R = ideal gas constant
T = temperature

The sigma (Σ) is a mathematical symbol for summation.  For example, Σ_ia_i = a₁ + a₂ + a₃ +  ...

Q = mc*delta*T

q = heat
m = mass
c = specific heat capacity
ΔT = change in temperature
ΔH = change in enthalpy
H^o_f = standard enthalpy of formation

*delta*H = *sigma* nH^*degree*_f[P] - *sigma* nH^*degree*_f[R]

This is Hess's law, which you should look up in your chemistry text or on wikipedia (http://en.wikipedia.org/wiki/Hess%27s_law)

[magnaflux]

Thanks for your help so far, what do you mean by specific heat capacity?

For molar mass, say I got water so that's 18.02 right? what would I write for the units

Also, to convert the molar mass in to grams what all do I need to know?

[Borek]

Thanks for your help so far, what do you mean by specific heat capacity?

http://en.wikipedia.org/wiki/Specific_heat_capacity

For molar mass, say I got water so that's 18.02 right? what would I write for the units

g/mol

Also, to convert the molar mass in to grams what all do I need to know?

Molar mass is already in grams.

Honestly, I have no idea how you are going to pass 

[Yggdrasil]

The value appearing below an element in the periodic table can be interpreted in two ways.  First, it represents the average mass of the element in atomic mass units.  For example, the average oxygen atom has a mass of 16amu (I say average because multiple isotopes of oxygen exist, and these isotopes have different masses).  The number can also be interpreted as the molar mass of the atom; that is to say, the mass of one mole of oxygen atoms is 16g (or put another way, 16g/mol).  Below, I will show that the two values are equivalent.

Given that the average oxygen atom weighs 16amu, a mole of oxygen atoms will have the mass:

16 amu * 6.02x10²³ = 9.63x10²⁴ amu

The conversion factor between grams and amu is 1g/6.02x10²³amu, so the mass of a mole of oxygen atoms in grams is:

9.63x10²⁴ amu * (1g/6.02x10²³amu)  = 16g

This conversion factor also allows you to calculate the mass of an oxygen atom in grams:

16 amu * (1g/6.02x10²³) = 2.66x10^-23g


In summary, 1g = 6.02x10²³amu is a very important conversion factor to know.

[magnaflux]

Thanks for your help so far, what do you mean by specific heat capacity?

http://en.wikipedia.org/wiki/Specific_heat_capacity

For molar mass, say I got water so that's 18.02 right? what would I write for the units

g/mol

Also, to convert the molar mass in to grams what all do I need to know?

Molar mass is already in grams.

Honestly, I have no idea how you are going to pass 

Yeah I'm not predicting much higher than a 40, but I'm hoping there'll be tons of question from early in the year that will seem easy to me now

[magnaflux]

The value appearing below an element in the periodic table can be interpreted in two ways.  First, it represents the average mass of the element in atomic mass units.  For example, the average oxygen atom has a mass of 16amu (I say average because multiple isotopes of oxygen exist, and these isotopes have different masses).  The number can also be interpreted as the molar mass of the atom; that is to say, the mass of one mole of oxygen atoms is 16g (or put another way, 16g/mol).  Below, I will show that the two values are equivalent.

Given that the average oxygen atom weighs 16amu, a mole of oxygen atoms will have the mass:

16 amu * 6.02x10²³ = 9.63x10²⁴ amu

The conversion factor between grams and amu is 1g/6.02x10²³amu, so the mass of a mole of oxygen atoms in grams is:

9.63x10²⁴ amu * (1g/6.02x10²³amu)  = 16g

This conversion factor also allows you to calculate the mass of an oxygen atom in grams:

16 amu * (1g/6.02x10²³) = 2.66x10^-23g


In summary, 1g = 6.02x10²³amu is a very important conversion factor to know.

Will the 6.02x10²³ be used for every situation when converting it?

[magnaflux]

failed the course by one percent... my dad will find out tomorrow.. this is not going to be good