Chemistry Stoichiometry

[karebear0684]

Never in undergrad was I ever expected to memorize molecular weights. This is biting me in the butt now, the only ones I know from memory are very basic, like H, C, O and N. There are lots of stoichiometry questions in the Kaplan book that I can set up fine, and could calculate fine if I knew molecular weights. Does anyone have any advice on which molecular weights are the most worth my time?

 

[Pharmaniac]

Never in undergrad was I ever expected to memorize molecular weights. This is biting me in the butt now, the only ones I know from memory are very basic, like H, C, O and N. There are lots of stoichiometry questions in the Kaplan book that I can set up fine, and could calculate fine if I knew molecular weights. Does anyone have any advice on which molecular weights are the most worth my time?

I'm pretty sure they give you those.

 

[bballa99]

Do they?

Oh god I've been memorizing them. Just a general rule of thumb, masses go up by ~1-2 AMU across the table, and in their families, they multiply by ~x2-2.5 going down.

 

[crazybob]

Never in undergrad was I ever expected to memorize molecular weights. This is biting me in the butt now, the only ones I know from memory are very basic, like H, C, O and N. There are lots of stoichiometry questions in the Kaplan book that I can set up fine, and could calculate fine if I knew molecular weights. Does anyone have any advice on which molecular weights are the most worth my time?

H-1, C-12, O-16, N-14, F-19, Na-23, Ca-40, Cl-35.5, P-31, S-32, U-238...

That's the only list of masses that I would be able to tell you from memory.

They should give you masses for anything other than those.

 

[bugg]

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