# chemistry

posted by Raina

1.)Calculate the number of moles in
3.50 x 10^21 atoms of silver. Show all work.

2.) Calculate the number of atoms in 2.58 mol antimony. Show all work

3.) Determine the mass of 1.45 mol FePO4. Show all work.

4.) Calculate the number of mol in 6.75 g of NaCl. Show all work.

5.) What is the volume, in liters, of 2.54 mol methane (CH4) gas? Show all work.

6.) What is the empirical formula of a compound that is 36.2% aluminum and 63.8% sulfur. Show all work.

Thanks so much!!! :)

1. Damon

A mol is 6*10^23 of anything, sort of like a dozen is 12 of anything
so
3.50 x 10^21 atoms (1 mol of atoms/6*10^23 atoms)

= (3.5/6) 10^(-2) = .58*10^-2 mol = 5.8 *10^-3 = .0058 moles

2. Damon

Now with that information and knowing that a mole of any chemical weighs its gram molecular mass I think you can do the rest
for example a mol of water, H2O has mass
2 H + O = 2(1) + 16 = 18 grams
so for water
18 grams is 6*10^23 molecules is one mole

3. DrBob222

4. mols = grams/molar mass

5. At what pressure? If you mean standard pressure of 760 mm Hg then you need to remember that 1 mol of gas occupies 22.4 L at STP

6. Take a 100 g sample which will be
36.2g Al
63.8g S.
Convert these to mols by mols = g/atomic mass.

36.2/27 = about 1.34
63.8/32 = about 2

Find the ratio. The easy way to do that is to divide both numbers by the smaller number. This makes the smaller number of the two exactly 1.0.
Al = 1.24/1.24--This is to get qet 1.00
S = 2/1.34 = 1.49
Obviously, the answer is NOT Al1S1.5 because we want whole numbers. But a 1:1.5 ratio also is 2:3 in whole numbers so the empirical formula is Al2S3.

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