Can you help me with my intro to chemistry homework?

There are a few questions I can t figure out and my professor hasn t responded to my emails.. I ve waited for 3 days and the homework is due tonight.

1. Calculate the number of moles of O2 required to react with phosphorous to produce 3.56 g of P4O6 (Molar mass P4O6=219.9 g/mol)

A. 0.097 mol

B. 0.111 mol

C. 0.0324 mol

D. 0.0486 mol

E. 0.0162 mol

2. How many electrons does the ion 35 17 Cl- have?

A. 16

B. 19

C. 34

D. 36

E. 18

(I thought the answer to this would be 17, but that s not an option..)

3. A sample of amonium phosphate contains .104 mol of nitrogen atoms. The number of moles in the oxygen sample is

A. .41 mol

B. .419 mol

C. 4.6 mol

D. .0104 mol

E. .139 mol

Any help is much appreciated!!! I was able to figure out the other 6 problems on this assignment, but I have no idea how to even approach these 3. Thank you!!!

Update:

I figured out that the answer to question 1 is D, but I'm still struggling with the other two

2 Answers

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  • Anonymous
    9 months ago

    3.56 g of P4O6 = 0.0162 moles.  From the formula, 1 mole of P4O6 contains 6 moles of O atoms so you  have 6 * 0.0162 moles.  A

     

    An atom of Cl has 17 protons since it's atomic number is 17.  If it was a neutral atom, it would have 17 electrons but since it's Cl-, it has one extra charge so you have 17 + 1 = 18 electrons.

     

     Formula for amonium phosphate is (NH4)3PO4.  So 1 mole of (NH4)3PO4 has 3 moles of N, 12 moles of H, 1 mole of P and 4 moles of O.  If you have 0.104 moles of N atoms, moles of O = 0.104 moles N * (4 moles of O / 3 moles N) = 0.1387 moles, E.

  • 9 months ago

    P4 + 3O2 ---> P4O6

    Three moles of O2 are required for every one mole of P4O6

    moles P4O6 ---> 3.56 g / 219.89 g/mol = 0.01619 mol

    0.01619 mol times 3 = 0.04857 mol

    answer choice D

    ===================

    See that minus sign on the Cl? That means one more electron than the atomic number. Answer choice E.

    ===================

    (NH4)3PO4

    See how the N to O ratio is 3 to 4. That's a molar ratio. In one mole of (NH4)3PO4, there are 3 moles of N and 4 moles of O

    Use a ratio and proportion

    3 is 0.104 as 4 is to x

    x = 0.1386667 mol

    answer choice E

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