Posts by A Canadian

Total # Posts: 104

Physics
(delta)Eg = -14.7J Therefore, Ek = -(delta)Eg = 14.7J I don't understand how you'd come to the above conclusion? Does Ek just always equal -(delta)Eg?

Chemistry
Reviewing for exams and completely forgot how to do this and looking back at my notes doesn't help for this one... Can you please explain how to assign oxidation numbers for Pb(OH)4^2- I guess what's confusing me is the hydroxide... I haven't come across brackets ...

Chemistry
How would you be able to recognise that C5H8 was an alkyne? And how would you know that CH3COCH3 was a ketone? (I thought it was an ether)

Chemistry
Apoarently the name of this compound is 4-ethyl-4-methylheptane: ........................CH3 ..........................| CH3-CH2-CH2-C-CH2-CH3 ..........................| .......................CH2 ..........................| .......................CH2...

Chemistry
I understood this at one point and now I'm confused again! :( What's the difference between 2,2-dimethyl and 2-ethyl? It's hard to find proper drawings online... For example, for naming CH3CH2C(CH3)2CH2NH2, Why wouldn't it be 2-ethyl-1-butanamine rather than 2,...

Chemistry
Sorry, I keep thinking of more stuff... Complications always magically arise right before an evaluation and never while I can actually ask my teacher :( Can there be more than three in a branch? So far we've only done ones with methyl, ethyl, and propyl, but is there a &...

Chemistry
Also, if there's branches coming off of it, what do you do? For example, if the left part had a branch: CH3 ...| CH3-CH2-N Or would that just be extending the branch? And it would make the "N-ethyl" into "N-propyl"?

Chemistry
................CH3 ..................| CH3-CH2-N-CH2-CH2-CH3 Hoping this turns out okay, but it's an amine and branching off of the N (on top) is a CH3. The name is N-ethyl-N-methylpropanamine but I don't get why. How do you know which ones to treat as branches? I ...

Chemistry
And how would you know if there's double bonds?

Chemistry
No, sorry, it'd be an ester right?

Chemistry
I'm having a lot of trouble with Naming organic compounds when given things like HCOOCH2CH2CH3. Can you recommend some steps? How do you identify the branches?? And would the example I have above be a carboxylic acid? My teacher said that it might help to just draw it out ...

Chemistry
And how would you know something was a cyclic hydrocarbon when given something like CH3CH2COOH? (I know that one isn't a cyclic hydrocarbon but I mean like when you get questions saying "name the organic compound" and they give stuff like CH3CH2COOH and CH3CONH2...

Chemistry
How do you draw N,N-dimethylheptanamine? The N,N part is confusing me most.

Chemistry
..........CH3...................................CH3 ............|..........................................| CH3 -- C -- C =(triple bond)= C -- C -- CH3 ............|..........................................| ...........CH3....................................CH3 Can't ...

Chemistry
Name each compound. /\/\NH2 (that's suppose to be a line diagram...) I got 1-pentanamine, but that's wrong. CH3CH2-O-CHCH2CH3 .....................| ..................CH3 I'm not sure how great this will turn out, but there's supposed to be a CH3 branching off ...

Chemistry
Explain why iron corrodes more quickly in seawater than in freshwater. I'm getting conflicting answers from searching on Google; is it because the corrosion of iron is a redox reaction, which involves a transfer of electrons, and therefore this transfer of electrons would ...

Chemistry
I forgot to write ^2 on the [I-] for Qsp. Just a typo though, I did square it when I punched it in my calculator.

Chemistry
20.00mL of a 1.100E-4 mol/L Pb(NO3)2 is mixed with 80.00mL of 4.450E-2 mol/L CaI2. Will a precipitate form? Here's what I did... [Pb2+] c=n/v = (1.1E-4 mol/L x 0.02L)/(0.02L + 0.08L) = 2.2E-5 mol/L [I-] c=n/v = (4.45E-2 mol/L x 0.08L)/0.1L = 3.56E-2 mol/L Qsp = [Pb2+][I...

Chemistry
I need help starting this question... A buffer solution is prepared by adding 30.0g of pure acetic acid to 41.0g of sodium acetate in water, and then diluting the solution to 1.00L. What is the pH of the buffer solution?

Chemistry
Okay, I feel like this question should be really easy because it's a multiple choice question but how do you figure it out?? I'm completely drawing a blank. Consider the following equilibrium N2O4(g) <-> 2NO2(g) Kc = 4.8E-3 Which set of concentrations represents ...

Chemistry
I'm reviewing for a test and I'm on Le Chatelier's principle. Decreasing the temperature of an exothermic reaction shifts the equilibrium to the right? I understood this weeks ago but now I can't remember. Wouldn't decreasing the temperature cause there to ...

Chemistry
The Ksp for nickel(II) hydroxide is 5.47E-16. What is the base dissociation constant for nickel(II) hydroxide? So I started off doing Ni(OH)2 (s) <-> Ni2+ (aq) + 2OH- (aq) I ..........................0 .................0 C ........................+x ................+2x E...

Chemistry
I need help starting this question: A buffer solution is prepared by adding 30.0g of pure acetic acid to 41.0g of sodium acetate in water, and then diluting the solution to 1.00L. What is the pH of the buffer solution?

Chemistry
I'm trying do this question: 0.10 mol/L hydrochloric acid is titrated with 0.10 mol/L methylamine, CH3NH2. Calculate the pH of the equivalence point. I'm having trouble with the equation... How do you know what HCl + CH3NH2 will produce? Is there a rule or something ...

Chemistry
Oh, are the other three salts? And you just have to see whether they're acidic or basic or neutral salts? I got that KNO3 was neutral, CaF2 was basic and NH4NO3 was acidic? So.. Ca(OH)2, CaF2, KNO3, NH4NO3, HNO3? Is there another way I should be doing this or is the salt ...

Chemistry
Ca(OH)2, CaF2, NH4NO3, KNO3, HNO3 - Arrange the solutions from most basic to most acidic. I know Ca(OH)2 will be most basic and HNO3 will be most acidic, but how do you determine for the other ones?

Chemistry
Oh okay so they have two distinct jobs, but they're still together in the solution? For example in a lab or something, both chemicals would be mixed inside one beaker? Is this explanation right?: If an acid is added, the H3O+ ions will be removed by NaHCOO, which produces ...

Chemistry
Sodium methanoate, NaHCOO, and methanoic acid, HCOOH, can be used to make a buffer solution. Explain how this combination resists changes in pH when small amounts of acid or base are added. Buffers kind of confuse me and I'm not sure how to start this. Can someone help me ...

Chemistry
The example problem I gave is the root of all my confusion... Before, I always though when you do Q=mc(deltaT), you're getting the amount of heat absorbed/released by the SURROUNDINGS, and so when you want to get deltaH, you'd have to make Q negative in order to get ...

Chemistry
In the equation Q = mc(deltaT), I learned that Q means heat transfer. Is it the heat transfer from the system to the surroundings, i.e. the system loses/absorbs heat or is it from the surroundings to the system? A couple of places on the Internet say that Q is the heat energy ...

Chemistry
Factors affecting reaction rate. Use collision theory to explain. Factor: nature of the reactant Affect on rate: more or less reactive based on its chemical identity. reactivity: aq>g>l>s Explanation: For the other factors, we had to explain it based on whether the ...

Chemistry
50 mL of copper(II) sulfate reacts with 50 mL of sodium hydroxide. Their concentrations are 0.3 M and 0.6 M respectively. The temperature increased to 23.6 C from 23.4 C. Determine the enthalpy change for the reaction in kJ/mol of sodium hydroxide. Q=mcΔT =(50g + 50g)(4....

Chemistry
Can someone check my answers please? I had specific trouble with 7, 13, and 27 (I'm pretty sure my other answers are correct; some reassurance would be nice though). And I have a small question about 8. 1. The ΔHf of an element in its standard state is defined to be 0...

Chemistry
for an assignment I'm writing, I'm trying to find the % efficiency of ethanol. We were given a chart that says ethanol's energy input (MJ/L) is 16.16 and its energy output is 23.58 % efficiency = energy output/energy input x100, so 23.57/16.16 x 100 I get 146%. So ...

English/Grammar
and if another "that" was added then "to" would change to "must", I guess?

English/Grammar
Maybe another "that" after "requires"?? The "...that ____ that..." bothers me though. Too many 'that's!

English/Grammar
There's something wrong with this sentence but I can't put my finger on it!! The federal government has put into effect a mandate that requires all gasoline in Canada to contain 5 percent ethanol.

Physics
I'm having trouble with motion graphs. How do you go from an acceleration-time graph to a velocity-time graph or displacement time graph? I know that to go from v-t to a-t I just take the slope of the v-t graph, but how do you do it the other way around?

Physics
A horse runs 15 m [N 23° E] and then 32 m [S 35° E]. What is the total displacement of the horse? I can't even visualise this... My friend told me the basic steps on how to solve it, but I got the wrong answer anyways... d1 = 15 m [N 23° E] d1x = 15m sin 23°...

Chemistry
Mg + 2HCl -> MgCl2 + H2 Over an interval of 1.00s, the mass of Mg changes by -0.011g What is the corresponding rate of consumption of HCl (in mol/s)? I got 9.0E-4 mol/s and that's the right answer. But I'm having problems with the next question. Calculate the ...

Grammar
(which is why I put it under English this time, rather than chemistry)

Grammar
I actually already got one to read it and he said, "I see nothing 'wrong'." so I guess nothing "wrong" with quotes would mean there are some technical issues or something, I don't know. but this time around I was loOking more for a grammar check...

Grammar
That's alright, thanks though.

Grammar-Writeacher
Hi Writeacher, I was wondering if you could take a look at my question jiskha(dot)com/display.cgi?id=1361488610 I don't know if you already have and decided not to answer it (never mind if you already did look at it), it's just that I've seen you edit some other ...

English
If it is feedback on only a small portion of it which could be read quickly, then thank you, but it did not come off that way.

English
I don't mean to sound rude, but you couldn't have read that all in less than a minute and so you couldn't have truly come to that conclusion. Please don't give false feedback.

English
This is a chemistry lab report, but I was wondering if someone could edit the grammar and look at the sentence structure, etc. I know it's really long and boring, but even if you just look over a bit of it, I would really appreciate it. And I'm assuming you don't ...

Chemistry
Thanks; I obviously got it wrong, but what was my teacher talking about when she said that when you have a solid reacting, you don't use the mass of the solid for Q=mc(deltaT), only the mass of liquids or solutions? Why wouldn't that apply in this case?

Chemistry
I had a quiz today and one of the multiple choice questions was something like, "find the final temperature of aluminum when it is cooled" and then it gave you the specific heat capacity of aluminum, the mass of the aluminum, initial temperature, and enthalpy change...

Chemistry
That's what I don't really understand. If it's of the total reaction, shouldn't you add, in my example, the moles of both reactants? i.e. 0.025 +0.025 = 0.05 mol. Then use that value when doing deltaH = -Q/n? How come you only use The moles of one?

Chemistry
So if you find the enthalpy change for one reactant, it's the enthalpy change for the other reactant (and products??), i.e. you know the enthalpy change for the entire reaction? So enthalpy change of one reactant (or product also?) = enthalpy change of entire reaction?

Chemistry
You know how when you do calculations for the enhaloy change of a reaction you start sort of like this?: NH3(aq) + HCl(aq) → NH4Cl(aq) 25 mL 25 mL 1.0 mol/L 1.0 mol/L n = c x v = 1 mol/L x 0.025L = 0.025 mol How come you only need the moles of one of the reactants? I ...

Chemistry
Oh, oops ! I forgot to put x100 and then the rest of my answer, 4.8% (or 5%) I think it's a small miracle that I didn't make any mistakes when calculating the enthalpy of formation, there were a ton of steps! Thank you so much!

Chemistry
Can you check my calculations, please? It's for a lab we did in order to find the the enthalpy of formation of NH4Cl(s). My final answer was -299.4 kJ, while the theoretical, or actual, value is -314.4 kJ. It was the closest value out of everyone in the entire class. I'...

Chemistry (DrBob222)
Oh no! :( I tried to sum up the stuff as best as I could and be brief since I felt that two pages was way too long, but now I feel like I shouldn't have done that... I'll ask her tomorrow how much detail she expects, etc. because I don't really think mine is okay...

Chemistry (DrBob222)
Hi, here's my (almost) 2-paged lab report introduction (hopefully you remember it from yesterday). I went to class today, and actually a lot of my other classmates' introductions were over 2 pages! Now I'm feeling kind of insecure about mine, and I'm not even ...

Chemistry
Firstly, is this right?: Exothermic reactions have a negative enthalpy change value because the enthalpy of the reactants are greater than the enthalpy of the products *since the reactants have weaker bonds.* (especially the starred part, I'm wondering about) If so, how ...

Chemistry
I thought it might be kind of obnoxious of me to just post two pages worth of stuff and ask someone to read it, but thank you so much for being willing to look at it, I'll definitely repost tomorrow! Thanks for answering, and good night!

Chemistry
I wrote an introduction for a lab report for the first time, and I was given no samples (my teacher said "feel free to ask your friends who had chemistry last semester if you can see their introductions... none of my friends took it last semester, so I have no one to ask...

Chemistry
Why wouldn't you do this reaction directly in a lab (and would rather use Hess' Law to determine the enthalpy of formation)?: 1/2N2(g) + 2H2(g)+ 1/2Cl2(g) -> NH4Cl(s) I don't think the reactants are that dangerous...? It's still pretty safe to do in a lab, ...

Chemistry
But that would happen AFTER a reaction... Why would a reaction end up being expthermic if, originally, the enthalpy of the reactants are greater than the enthalpy of the products. And also, why do weaker bonds have more enthalpy/energy?

Chemistry
Why is the enthalpy of the reactants greater than the enthalpy of the products in an exothermic reaction? If it has something to do with the reactants having weaker bonds, why do weaker bonds have higher energy/enthalpy? It doesn't really make sense to me that weaker bonds...

Chemistry
I'm basically trying to explain why, in exothermic reactions, enthalpy of the products are greater than the enthalpy of the reactants (resulting in a negative enthalpy change). And I obviously don't know myself. Can someone please explain? I can't seem to find the ...

Chemistry
I'm trying to write a sentence like this: Exothermic reactions have a negative enthalpy change value because the enthalpy of the reactants are greater than the enthalpy of the products since the reactants have weaker bonds.... Why do weaker bonds have higher energy/...

Chemistry
It's just that I have to include both ideas together in a paragraph and I writing, "Energy is required to break a bond. Breaking a bond requires energy." doesn't have "flow" and would work better in one sentence.

Chemistry
Basically, ignore the rest of my question if the above sentence is okay.

Read this before the question!
Sorry, I think this sentence should be alright, "Energy is required to break bonds, and when the bonds break, energy is absorbed." Don't know why I had to go through all that trouble to reach this simple sentence, but...

Chemistry
This question came up because I'm trying to write for the introduction in my lab report, "Energy is required to break bonds, so when bonds break, energy is absorbed". But that sounded off (because that's like saying the absorption of energy when bonds break ...

Chemistry
i.e. is energy absorption a result of breaking bonds, or is energy absorbed in order to break bonds? So like... Energy is required to break bonds. Energy is somehow obtained, the bonds break... and this results in the absorption of *different* energy (which is unrelated to the...

Chemistry
Is this right?: Energy is absorbed in order to break bonds because bond breaking requires energy. Or are these two statements completely separate?: "energy is absorbed when bonds break" and "breaking bonds require energy"

Chemistry
Had a recent mix-up when I re-read my chemistry notes, and trying to clear things up properly; is this right?: When bonds form, energy is released, and so the reaction absorbs energy. I have two different things written... a bond breaking results in energy absorption, breaking...

Physics or math (very simple terminology question)
"Describe the characteristics of each graph (for example, . . . ., zero or non-zero intercept value)." I guess a zero intercept value would be if the line is on the point (0,0)/the origin. But what if the line starts at (0,1) or (2,0). Because then the x intercept is...

Chemistry
So for the neutralisation one I'm way off, right? Is it unacceptably off? Because my teacher said we'd have tomorrow to continue if we didn't finish, so I might just do that part again. That makes more sense, thanks so much for answering (for all the other times ...

Chemistry
I did a lab today in class and part of the lab is to experimentally find the enthalpy for the dissolution of ammonium chloride by dissolving 4.0 g of NH4Cl(s) in 50.0 mL of H2O(l). I got a -5°C temperature change and calculated delta H to be 15 kJ/mol. According to the ...

Chemistry
Someone said, "Calculate the total delta H of the reaction and subtract the total delta H of the product from it. If you get a positive value, it radiates heat which means it's exothermic. If it is negative, heat is needed to get a reaction so it is endothermic."...

Chemistry
C6H14 + 19/2 O2 -> 6 CO2 + 7H2O delta H = -4163 kJ What mass of hexane is required to produce 1.0E5 kJ of heat by complete combustion? -4163 kJ/mol x mol C6H14 = 1E5/-4163 kJ/mol Mol = 1E5/-4163 kJ/mol Mol = -24 mol I know I can do m=n x MM now, but shouldn't the value ...

Chemistry
Someone said, "Calculate the total delta H of the reaction and subtract the total delta H of the product from it. If you get a positive value, it radiates heat which means it's exothermic. If it is negative, heat is needed to get a reaction so it is endothermic."...

Chemistry
HCl (aq) + NaOH (aq) -> NaCl (aq) + H2O (l) Will the neutralisation reaction be endothermic or exothermic? Hint: think about the net ionic equation. So, taking the hint, I got: OH- + H+ -> H2O Not sure how that helps, and now I'm stuck; how would I figure out if this...

Chemistry
Sorry, how would you solve for mols? I feel like this should be obvious, but ...

Chemistry
Are my answers correct? C6H14 + 19/2 O2 -> 6 CO2 + 7H2O enthalpy change = -4163 kJ a) if 0.537 mol of carbon dioxide is produced in the reaction represented by the equation above, how much heat is released by the reaction? Enthalpy change = 0.537 mol CO2 x -4163kJ/6 mol CO2...

Chemistry
If you absolutely had to improve it what would you improve? Anything that sticks out especially to you But thank you; haha, I wouldn't go after an American prize anyways!

Chemistry
2C2H2 + 5O2 -> 4CO2 + 2H2O + energy What does the equation communicate about the relative energy of the chemical bonds in the reactants and products? The intermolecular bonds of the reactants are weaker than that of the products' because the products' intermolecular...

Chemistry
I checked it over for what feels like the tenth time and I see that I should've converted the 3.82 kJ to 3820 J; I ended up with the correct answer using that. But I feel like my method was a bit over-complicated. Is there a simpler method that I'm just overlooking?

Chemistry
I just realised I made the stupidest mistake ever. I guess this is what happens when you try to do chemistry while sick. The last bit of math doesn't make sense; it should be 3.82 = (460.24)(Tf-21.4°C) 3.82 = Tf460.24 - 9849.136 -Tf460.24 = -9849.136 - 3.82 Tf = -9852....

Chemistry
Please help me figure out where I went wrong. HNO3 + KOH -> KNO3 + H2O enthalpy change = -53.4 kJ/mol 55.0 mL of 1.30 mol/L solutions of both reactants, at 21.4°C, are mixed in a calorimeter. What is the final temperature of the mixture? Assume the density of both ...

Chemistry
, but then would 1mol/18g H2O mean 1 mol per 18 grams per mol of H2O..? There's one mol for every 18g of H2O..? It's confusing

Chemistry
But I don't think division would mean "which" weighs 18g..

Chemistry
I don't really understand why unit analysis works. I found a simple example on a website (I can post the link in a comment if you want). It says, For example, convert 18 grams of water to moles. The molar mass of water is 18 g/mol; therefore : 18g H2O x 1 mol/18g H2O = 1 ...

Chemistry
 4Fe + 3O2 -> 2Fe2O3 + 1.65E3 kJ  C) what is the enthalpy change for the formation of 23.6 g of iron(iii) oxide?  I'm trying to understand thermochemical reactions and stoichiometry, so could you please tell me if this is correct? And please explain the ...

Chemistry
25.9 kJ + 1/2 H2 + 1/2 I2 -> HI B) how much energy is needed for the reaction of 4.57E24 molecules of iodine, I2, with excess hydrogen, H2? How does the "excess" hydrogen come into play? I mean, what's the significance of having excess H2 and how do I figure ...

Chemistry
4Fe + 3O2 -> 2Fe2O3 + 1.65E3 kJ C) what is the enthalpy change for the formation of 23.6 g of iron(iii) oxide? I'm trying to understand thermochemical reactions and stoichiometry, so could you please tell me if this is correct? And please explain the parts that I ...

Chemistry
I'm really sorry, but I still don't really understand - what do you mean by "figure out what part of two moles you had "?

Chemistry
Thanks for answering!! "Now for 23.6g FeOxide, you do not have two moles, you have to figure what part of the energy you get." Could you clarify what you mean by that? I think this is closer to answering and fixing my confusion; what do you mean by "what part of...

Chemistry
Sorry, I posted the above before I got to see your answer, bobpursley. I think I get it a little more but could you clarify a bit more based on what I asked above?

So very confused :(
Okay so after some trial and error (I just kept trying different things Until I got the answer), I figured out it's *probably* solved like this: Enthalpy = 23.6g Fe2O3 x 1 mol Fe2O3/[(2x56) + (3x16)]g x -1.65x10^3 kJ/2 mol Fe2O3 = -1.22 x 10^2 kJ If that's right, my ...

Chemistry
This isn't exactly a homework question, I'm just trying to understand the concept we learned today... So say we had: 4Fe + 3O2 → 2Fe2O3 + 1.65 x 10^3 kJ Does that mean for every 4 mol of Fe, 3 mol of O2, and 2 mol of Fe2O3 we have 1.65 x 10^3 kJ? And if I were to...

Chemistry
N2 + O2 -> 2NO enthalpy change = +180.6kJ c) what is the enthalpy change for the formation of one mole of nitrogen monoxide? Okay, I know this question is super easy, but I don't know how to do it; if someone could please give me a detailed explaination on how to do a ...

Chemistry
How come the formula for potassium peroxide is K2O2; I can't see how you'd get that...

Chemistry
Why is the formula for potassium peroxide K2O2?

Math
 The height of a plant after each of the first three weeks was 7mm, 20mm, and 33mm, respectively. If this pattern of growth continues, in what week will the plant be more than 100mm tall?  The answer is 9 weeks.  This is what I did, and it's clearly wrong:&...

  1. Pages:
  2. 1
  3. 2
  4. Next>>