Chem--how the hell do you know

[pmarank]

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Okay guys how do you learn some stuff in chemistry? Like how do some people just know stuff about chem even though they have never taken it before?? I know i sound really vague so let me elaborate...

we were given a problem about finding the pH of lik .1 M NH4Cl
It was pretty obvious for me to know that Cl was the conj. base of HCl so i knew it wouldnt affect the pH but i have NO IDEA how some ppl realized that NH3 was a weak base and how this related to the problem...

i figured things out but i still dont understand how we are just expected to know that NH3 is a weak base...it seems like there are millions of weak bases how are we suppose to know specific ones?!?

 

[DrYoda]

In the case of NH3, it's just a really common weak base. It's used in all kinds of example problems.

I imagine your book has a table of some sort with common weak bases/acids.

 

[Dial71]

First, this forum isn't for homework questions. Your thread may be closed.

Second, chill out.

Third, read the $%#& book. Failing that, pay someone to read it to you. It will probably cost you $25-30/ hour for a private tutor.

P.S. Most doctor are bad at chemistry.

 

[Mithril]

.

 

[Snarkalark]

they took chem in high school and paid attention? there's lots of stuff that they tell you to memorize, which i never did. as long as you can reason out the information given to you, it'll be okay.

also, as someone said, nh3 is a really common weak base that you'll see about 100 times in your course and after that much exposure, you'll "just know" it too.

 

[Isoprop]

Okay guys how do you learn some stuff in chemistry? Like how do some people just know stuff about chem even though they have never taken it before?? I know i sound really vague so let me elaborate...

we were given a problem about finding the pH of lik .1 M NH4Cl
It was pretty obvious for me to know that Cl was the conj. base of HCl so i knew it wouldnt affect the pH but i have NO IDEA how some ppl realized that NH3 was a weak base and how this related to the problem...

i figured things out but i still dont understand how we are just expected to know that NH3 is a weak base...it seems like there are millions of weak bases how are we suppose to know specific ones?!?

That's actually a good question! Asking these sort of questions is important when learning about chemistry. SO GO ASK YOUR PROFESSOR; it may be super obvious to everyone else, but YOU ARE NOT ALONE.

To answer your question--there is a list of strong bases just as there is a list of strong acids. Anything that is not a strong base that has at least one electron pair to accept protons is a potential weak base. However, conjugates of strong acids have no acid-base properties.

Now even though I answered your question, I urge you to not hesitate to ask questions to your prof or TA or other classmates even if something seems obvious to everyone else but you. I also recommend getting a chemistry tutor (usually, chem tutors are available for free at most schools) if you are really lost.

Good luck!

 

[ReptarBar]

you don't deserve to pass if you don't know what ammonia is.

 

[PremedGunner]

fa

 

[truthis]

A textbook from a school bookstore will give you a lot of info for studying them just by your brain power, just you have to be wary of whats out there.
An example from my G chem textbook: their measurement on blood Ph level was way out of date, last time I was wondering (because I'm a nerd.)where did they get that info, it turned out after some googling, they just plain downloaded it from some outdated website. That number first apppeared on a paper published by a very noble person in the science community who happened to have the same last name as mine.
whats funny was that number was emphasized MULTIPLE times throughout the whole textbook. 😀

so its good to be aware of the scources of info.

Okay guys how do you learn some stuff in chemistry? Like how do some people just know stuff about chem even though they have never taken it before?? I know i sound really vague so let me elaborate...

we were given a problem about finding the pH of lik .1 M NH4Cl
It was pretty obvious for me to know that Cl was the conj. base of HCl so i knew it wouldnt affect the pH but i have NO IDEA how some ppl realized that NH3 was a weak base and how this related to the problem...

i figured things out but i still dont understand how we are just expected to know that NH3 is a weak base...it seems like there are millions of weak bases how are we suppose to know specific ones?!?

 

[truthis]

if the "experience" exists. lol.

Real life experience can also play a role.

 

[truthis]

yeah, you'll know it after being shown 100 times by the same teacher.
next time the "fact" shows up, you'll know what your teacher has taught you..

they took chem in high school and paid attention? there's lots of stuff that they tell you to memorize, which i never did. as long as you can reason out the information given to you, it'll be okay.

also, as someone said, nh3 is a really common weak base that you'll see about 100 times in your course and after that much exposure, you'll "just know" it too.

 

[chiapet874]

you don't deserve to pass if you don't know what ammonia is.

I chuckled.

Most likely experience from other classes has led the other students to their conclusion.

 

[truthis]

some you know after the teacher lecture you on the content of his own assigned textbook. reading the textbook only gives you 80% of grasp of some really important concepts and mechanisms.

Okay guys how do you learn some stuff in chemistry? Like how do some people just know stuff about chem even though they have never taken it before?? I know i sound really vague so let me elaborate...

we were given a problem about finding the pH of lik .1 M NH4Cl
It was pretty obvious for me to know that Cl was the conj. base of HCl so i knew it wouldnt affect the pH but i have NO IDEA how some ppl realized that NH3 was a weak base and how this related to the problem...

i figured things out but i still dont understand how we are just expected to know that NH3 is a weak base...it seems like there are millions of weak bases how are we suppose to know specific ones?!?

 

[apumic]

Most people are simply familiar with ammonia; however periodic trends also come to mind.... You should have learned basic periodic trends in G-Chem I. (I know our students learn them right around the 3rd or 4th chapter of the book, like a month into class.) You know NH3 must be basic because its central atom (N) is to the left of H2O and it is presumably in an aqu (H2O) soln, so NH3 will donate electrons to the H2O. (This does not hold true between NH3 and CH4 as CH4 lacks a lone pair; however CH3–>>NH2->>OH-.)

 

[DM3]

I don't mean to pick on the OP, but these pre-meds absolutely LOSING THEIR MINDS in GCI make me laugh.

Reminds me of the class after our second GC exam, when the president of Pre-Med AMSA came in before lecture and asked how many pre-meds there were in the room and 90% of my 250+ classmates raised their hand, only to have the professor walk in two minutes later and tell everyone the class average was a 47%.

Boy, those damn electron configuration problems sure are a bitch ; D

 

[Envix]

I remember in organic chemistry II our professor would put 4 compounds on every exam and ask, what is the pKa of this, + or - 2? You would think it to be impossible to just know, but you just plain out started remembering the different functional groups to start from and how different parts of the compound would modify it slightly. I still remember the basic starting points that CH4 is around 35, a COOH group around 4, and an alcohol group around 10-12, and I took it years ago.

Same thing with gen chem. Yes, you can memorize the tables or have an actual concept as to the reason why certain things dissociate in water and others don't, but the way most people do it is just by seeing and doing enough examples that they just remember. Ammonia is probably one of the 2-3 most common examples of a weak base, so you see it a lot.


tl;dr: do lots of practice problems.

 

[Lunasly]

NH3 was one of the only bases we learned and used in Chemistry in my senior year of highschool. :\

 

[miabullitt]

Which chem class is this? Chem 2?

 

[Chew]

NH3 was one of the only bases we learned and used in Chemistry in my senior year of highschool. :\

Hmm.....the only bases I learned in high school were first and second base.

 

[HW51Revisited]

Hmm.....the only bases I learned in high school were first and second base.

zing

 

[pmarank]

Which chem class is this? Chem 2?

its chem I

 

[cheesier]

.

 

[mspeedwagon]

When I took chem I people had this reaction. How are you so good naturally in chemistry? The truth is, I wasn't. I had taken AP chem (even though I claimed otherwise) and had seen a lot of it before. I had learned to identify strong acids/bases and such things that people that saw it for the first time were struggling with. The key is a combination of reading the book/understanding/memorizing and problem solving. You need to learn to do all four to be successful in your chemistry career. Good luck.

Okay guys how do you learn some stuff in chemistry? Like how do some people just know stuff about chem even though they have never taken it before?? I know i sound really vague so let me elaborate...

 

[Isoprop]

What really bothers me about this thread is that a lot pf people just sh** on OP not "naturally" knowing that ammonia is a base. And it's f***ed up is that a lot of people just answered with "just know it." The people who ask "how do you know ____" or "why does _____ happen" are the ones who are really worth teaching.

To OP: keep it up! You are asking good questions. Trying to develop a deeper understanding will help in future classes and on the MCAT. Remember, general chemistry is a pretty challenging freshman class. I think some of us have forgotten that since we take what we learn for granted sometimes.

 

[once]

the people who "just know" might have drilled this bit of info into their memories by prior exposure to the course, or they are using some logic to figure out that it is a weak base because of the happiness of nitrogen when it has zero as a formal charge. When this happens it doesn't want anything to do with another proton.

 

[gravitywave]

it's also just a fact that some people are quicker on the uptake in terms of figuring out trends, as opposed to just blindly memorizing facts. not me though, i hated acid-base chem with a passion.

 

[hiyaman]

That's actually a good question! Asking these sort of questions is important when learning about chemistry. SO GO ASK YOUR PROFESSOR; it may be super obvious to everyone else, but YOU ARE NOT ALONE.

To answer your question--there is a list of strong bases just as there is a list of strong acids. Anything that is not a strong base that has at least one electron pair to accept protons is a potential weak base. However, conjugates of strong acids have no acid-base properties.

Now even though I answered your question, I urge you to not hesitate to ask questions to your prof or TA or other classmates even if something seems obvious to everyone else but you. I also recommend getting a chemistry tutor (usually, chem tutors are available for free at most schools) if you are really lost.

Good luck!

This. To the OP, chemistry isn't that difficult to learn if you put in the time and effort. You don't have to like it but if you want to do well in it you sure as hell have to try.

 

[circulus vitios]

It's been like that in every chemistry class I've taken (organic, gen chem, quant. analysis.) It's why I switched majors. Chemistry professors like to pretend there are concepts and rules in chemistry. There are, but they're untrue more often than they are true.

 

[DM3]

What really bothers me about this thread is that a lot pf people just sh** on OP not "naturally" knowing that ammonia is a base.

It's absurd to suggest anyone 'just knows' anything about Gen Chem. Obviously we all learned somewhere. I don't know the OP personally, but I tutor a lot of GC and OC students, and have come to notice certain frustrations often accompany certain behaviors, or lack of certain behaviors.

I can't begin to count the students who will lament about how difficult a class or concept is, or how unfair a professor is ect ect. But I've found that, almost invariably, these students have not read the book at all, much less prior to lecture, not done the problems available to them, skip class, wait until the weekend before the exam to read over slides (heaven forbid they have actual notes to review).

Fact of the matter is, if these kids (because that's what they are) spent a tenth of the time trying to actually learn chemistry that they do looking for shortcuts and a hand to hold we wouldn't have posts like these on SDN (I'd also prolly be out of a job). What they don't realize is if you spend the time to really *understand* chemical behavior now, classes like Biochemistry and Organic become a breeze because you can predict what will happen in a reaction using what you know about basic molecular properties like electronegativity.

Again, I don't know the OP, so I can't direct this at him/her, but I strongly encourage every freshman telling the world he/she is going to be a heart surgeon while insisting that Halloween Parties and tailgating take precedence over the midterm on Tuesday to take a long look in the mirror.

As the sign behind my department's advisor reads "If God put you here to be a doctor, why didn't he give you the ability to pass chemistry?"

/end rant

 

[pmarank]

It's absurd to suggest anyone 'just knows' anything about Gen Chem. Obviously we all learned somewhere. I don't know the OP personally, but I tutor a lot of GC and OC students, and have come to notice certain frustrations often accompany certain behaviors, or lack of certain behaviors.

I can't begin to count the students who will lament about how difficult a class or concept is, or how unfair a professor is ect ect. But I've found that, almost invariably, these students have not read the book at all, much less prior to lecture, not done the problems available to them, skip class, wait until the weekend before the exam to read over slides (heaven forbid they have actual notes to review).

Fact of the matter is, if these kids (because that's what they are) spent a tenth of the time trying to actually learn chemistry that they do looking for shortcuts and a hand to hold we wouldn't have posts like these on SDN (I'd also prolly be out of a job). What they don't realize is if you spend the time to really *understand* chemical behavior now, classes like Biochemistry and Organic become a breeze because you can predict what will happen in a reaction using what you know about basic molecular properties like electronegativity.

Again, I don't know the OP, so I can't direct this at him/her, but I strongly encourage every freshman telling the world he/she is going to be a heart surgeon while insisting that Halloween Parties and tailgating take precedence over the midterm on Tuesday to take a long look in the mirror.

As the sign behind my department's advisor reads "If God put you here to be a doctor, why didn't he give you the ability to pass chemistry?"

/end rant

I actually spend a significant amount of time studying for chem. Truth is i spend more time on chem than any other class. Yet im getting As in everything except chem... Is it possible that im just better in the other, social science type, classes? Is it possible that those other classes are just simply easier? Is it possible that im just naturally bad at chem?--Yes, yes and yess

But i ont' give a ***GUKCK. I dont even know if i wanna be a doctor. I mean going into debt for med school and [insert reasons why being a doc sux here]...who the hell wants all that? I jus wanna fraking decent grade in chem, ery1 else (aka just u) can go f em selves --->I dont even hate the class, subject, or professor ITS JUST FRUSTRATING WHEN YOU STUDY MORE THAN YOU HAVE EVER STUDIED FOR ANYTHING ELSE JUST TO COME OUT WITH A C+ ON EVERY EXAM

And whats this BS about going to the friggen airport to get felt up by the tsa... Dont even get me started on those damn liberals

^ thats what i feel...thats poetry... when do i get published and then get some freaking money so i can buy a WRX or Evo already?

 

[DM3]

I jus wanna fraking decent grade in chem

Oh see I didn't realize you *really really really wanted* to do well. In that case the teacher should just give you an A.

 

[Self]

I actually spend a significant amount of time studying for chem. Truth is i spend more time on chem than any other class. Yet im getting As in everything except chem... Is it possible that im just better in the other, social science type, classes? Is it possible that those other classes are just simply easier? Is it possible that im just naturally bad at chem?--Yes, yes and yess

But i ont' give a ***GUKCK. I dont even know if i wanna be a doctor. I mean going into debt for med school and [insert reasons why being a doc sux here]...who the hell wants all that? I jus wanna fraking decent grade in chem, ery1 else (aka just u) can go f em selves --->I dont even hate the class, subject, or professor ITS JUST FRUSTRATING WHEN YOU STUDY MORE THAN YOU HAVE EVER STUDIED FOR ANYTHING ELSE JUST TO COME OUT WITH A C+ ON EVERY EXAM

And whats this BS about going to the friggen airport to get felt up by the tsa... Dont even get me started on those damn liberals

^ thats what i feel...thats poetry... when do i get published and then get some freaking money so i can buy a WRX or Evo already?

You're up ****'s creek, buddy. Do yourself a favor and get a nice and easy social science degree then go and make 40k a year.