can you please double check my answers...(moles)??

Question

1) How many grams of carbon are in 15.3 moles of tricarbon tetrahydride? (550.8 grams of C)

2) How many litres are in 0.00923 grams of O2(g)?
(6.5 x 10^-3)

3) How many moles of Br2(l) are contained in 250.0 mL of Brd(l) ? d= 0.72g/mL?
(1.13 moles of Br)

4) What is the density of NH3(g) at STP?
(0.758 g/L)

5) What is the molar mass of Al2(C2O4)3 x 4H2O?
what is the answer to this??? don't get it?

6) What is the volume of 9.2 x 10^25 molecules of SbH3(g) at STP?
I also don't get this one, please help, thanks!

Answer 1

#1 is correct:15.3 x (12 x 3)

#2 0.00923g/32g/mol x 22.4 l/mol = 0.00646 (you're OK)

#3 I don't know the compound Brd, maybe a typo, but

250.0ml x 0.72g/ml 1mole Br2/160g = 1.125 moles Br2 (or 2.25 moles Br). So you're OK

#4 correct (17g/mol/22.4l/mol)

#5 To do this you just need to add up all the weights for component atoms: I presume the x4H2O is 4 waters of crystalization.

{(2 x 27) + 3 x [(2 x 12) + (4 x 16)] + 4 x [(2 x 1) + 16]}

= 54 + 264 + 72 = 390g/mole

#6 To do this one, you need to determine how many moles you have, and multiply by 22.4liters/mole to get volume (in liters).

[9.2 x 10^25/6.02 x 10^23]moles x 22.4l/mole

The calculator I got doesn't do the exponents; but you should be able to do it on yours (I think it will be about 150 moles for the first part of the equation).

Answer 2

5) You must add up the atomic masses (AM) of the components: 2*AM(Al) + 6*AM(C) + 16*AM(O) + 8*AM(H). This is 2*27 + 6*12 + 16*16 + 8 = 390

6) there are 6*10^23 molecules in one mole; so 9.2*10^25 molecules are 1.53*10^2 moles of SbH3. Use the gas law V = n*R*T/P for n = moles.