Hey, I have a few questions on some of the problems for my chem homework and any help on any of them would be greatly appreciated I tried to make it look as pretty as I could but it is still a little messy sry >.<


1) In an oxyacetylene welding torch, acetylene (C2H2) burns in pure oxygen with a very hot flame. How many grams of oxygen gas are required to react with 56.25 g of acetylene?

C2H2 + O2 CO2 + H2O (Hint: This isn't balanced)

2) Calculate the mass, in grams, of 0.324 moles of iodine pentafluoride.

These ones are multiple choice:
3) If I take an aspirin (C9H8O4) tablet containing 325 mg of aspirin, how many molecules of aspirin will I consume?

1. 3.52 x 1025 molecules
2. 3.00 x 10-27 molecules
3. 1.09 x 1024 molecules
4. 1.09 x 1021 molecules

4 ) ______ are in 10.0 moles of C10H 8.

1. 8.00 moles of hydrogen
2. 4.82 x 1025 atoms of hydrogen
3. 6.022 x 1024 atoms of carbon
4. 10.0 moles of carbon
5. 4.82 x 1024 atoms of hydrogen

5) What precipitate is formed in the reaction of aqueous Pb(NO3)2 with aqueous KI?



1. PbI2
2. KI
3. No precipitate is formed in this reaction.
4. PbI

6) Natural gas methane (CH4) burns in oxygen to yield water and carbon dioxide (CO2) as shown below:

CH4 + 2 O2 CO2 + 2 H2O

How many moles of carbon dioxide are produced from 3.8 moles of oxygen?


1. 3.8 mol
2. 7.6 mol
3. 2 mol
4. 1.9 mol


7) Which of the following statements is not true?


1. 10.00 moles of water contain 6.022 x 1024 molecules of water.
2. 10.00 moles of water and 2.000 moles of butane (C4H10) contain the same number of hydrogen atoms.
3. 10.00 moles of water and 10.00 moles of H2 contain the same number of molecules.
4. 10.00 moles of water contain 18.02 grams of water.
5. 10.00 moles of water and 5.000 moles of CO2 contain the same number of oxygen atoms.

8 ) When ammonia gas [NH3(g)] is passed over hot sodium, hydrogen gas is released and sodium amide, (NaNH2), is formed as a solid product. Write a balanced chemical equation for this process and be sure to indicate the state of each compound.

1. NH3(g) + Na(s) NaNH2(s) + H2(g)
2. 2 NH3(g) + 2 Na(s) 2 NaNH2(s) + H2(l)
3. 2 NH3 + 2 Na 2 NaNH2 + H2
4. 2 NH3 + Na 2 NaNH2 + H2
5. 2 NH3(g) + 2 Na(s) 2 NaNH2(s) + H2(g)

9) If I add 5.00 g of sucrose (C12H22O11) to my cup of coffee, how many moles of sucrose did I add?


1. 68.4 moles
2. 0.172 mole
3. 1710 moles
4. 0.0146 moles
5. 0.014620 moles

10) When I metabolize 50.0 g of sucrose, how many grams of CO2 do I produce?

C12H22O11 + O2 H2O + CO2 (Hint: This isn't balanced...)


1. 600 g
2. 0.536 g
3. 77.2 g
4. 6.43 g

is this the whole assignment? what parts do you have trouble with?

no these are just the problems I do not understand

no offense this looks like the whole thing copy pasted, but w/e

This is how you solve them, im not going to do them for you, but ill tell you how

1. balance equation, find moles of C2H2. multiply by mole ratio, mulitply by molar mass of oxygen
2. multiply molar mass*number of moles
3. find molar mass of aspirin, find moles of asprin, multiply num of moles * 6.022*10^23
4. guess and check (use 6.022 to convert moles to # molecules)
5. free one- its PbI2
6. multiply number of moles of oxygen by molar ratio between moles oxygen/moles CO2
7. you can do this if you did 1-6
8. just make sure everything is equal on both sides
9. divide grams/ molar mass of sucrose
10. balance equation, find moles of sucrose, find moles of CO2 produced, multiply moles of CO2 times molecular weight of CO2

It is not I typed out the problems I didn't understand I promise and thank you very much this is all I wanted since I'll need to know how to do them myself for the test

i'll get you started with the first one, but i agree with bean this looks like the whole assignment...

Here is the balanced reaction:

2C2H2 + 5O2 4CO2 + 2H2O

so for the first one it would be 69.13g?

56.25 g C2H2/26.04(Molar mass) = 2.16 mole acetyelene to be reacted

2.16 mol C2H2* (5 Mol O2/2MolC2H2) = 5.400 Mol O2 -> i got 5 and 2 from the balanced chemical equation

5.400 Mol O2 * 32 = 172.8 g is what i got

if you need help with any of them i can post it out what to do step by step but you should try to do them first. Also, if you post your thinking process and work you do i can tell you where you went wrong(if you do).

This post was edited by bean183 on Apr 22 2009 08:15pm

This may help with your molar conversions

Mass (grams) = (# of mols) (molar mass)

# of mols= Mass (grams)/ Molar Mass (grams/ mol)

And here's a nifty chart to show you the relationship between Molar Mass, Mols, and Representive Particles (This may of may now help you out)



This post was edited by PTRH on Apr 22 2009 10:19pm