[book_luvr]

So I have some chem questions that I'm confused about...

1) What is the molar mass of the following compound:
Ca(HCO3)2
I got 162.12 but I'm not sure if I did the steps correctly..

2)What is the mass of 1/75 mol of nitrogen?

3)How man molecules are contained in 2.45 mol of oxygen gas.

4) What is the mass of 2.45 X 1024 atoms of potassium

5)What mass of lead could be found in 126.8 g of lead (II) nitrate?

[ARGOS++]

Dear book_luvr;

  1.)  The number is correct, but you forgot the units!

Knowing you did number 1 correct; can you try the others and show us your work, if I give you the following Hint?:
            http://en.wikipedia.org/wiki/Avogadro's_number

Good Luck!
                    ARGOS⁺⁺

[book_luvr]

Thanks a lot for the help...i'll try the other ones right now and get back to you.

[book_luvr]

Okay i made a typo in number two..i meant to type 1.75 mol. ANyways, the answer i got was 24.5 grams. I don't think it's right though.

[ARGOS++]

Dear book_luvr;

Your result would be correct, if nitrogen would be mono-atomic, but nitrogen is:
       http://en.wikipedia.org/wiki/Diatomic#Description_and_occurrence_in_nature

Good Luck!
                    ARGOS⁺⁺

[book_luvr]

Ooooh yeah i forgot about that diatomic rule...okay so the correct answer would be 49g, right?

[ARGOS++]

Dear book_luvr;

That’s correct!

Good Luck!
                    ARGOS⁺⁺

[book_luvr]

Ahhhh  my god this questionhas been killing me i've been staring at if forever.

How many moles are contained in 135.6 g of propane gas (C3H8)?
I know i have to put avagadro's number to use somehow but i'm just super confused...?

[Las]

I dont think you need the avagadro's constant...You can do it with the molar mass only..right??

[book_luvr]

^Hmmm i think you're right well i attempted it and i got 290.88g

[Las]

Nope I dont think it should be that much...try using the units to find out what you have to multiply and what you have to divide..when its "g per mol", you multiply by mols to get g (mass) and likewise..I think its easier than using equations..

and I think it should be 3point something...

[ARGOS++]

Dear book_luvr;

For propane you must first know how much is its molecular mass, before you can get any other result.

Good Luck!
                    ARGOS⁺⁺

[book_luvr]

Okay my answer for that ques. is 44.08..?

[Las]

Nope..what's the molecular mass of C3H8 that you got?

[Las]

oh wait..sorry that's the molecular mass of C3H8 right?? so then you divide the mass (135.6g) by that,if I'm not mistaken..