Question

1) How many atoms are there in 51.3 g of barium chloride (BaCl2)?
2) How many moles of carbon monoxide (CO) are in 29.3 g of the compound?

3) What is the formula for copper(II) phosphate? Capitalization and punctuation count?

4) How many atoms of phosphorus are in 2.90 mol of copper(II) phosphate?

5) How many moles of N are in 0.191 g of N2O?

6) A sample of C3H8 has 7.68 × 1024 H atoms. How many carbon atoms does the sample contain? What is the total mass of the sample?

7) Calculate the percent composition by mass of each element in Al(OH)3. Use at least three significant figures.

% Al= ?,   % O=?   ,   % H =?

8) What is the empirical formula of a compound composed of 3.25% hydrogen (H), 19.36% carbon (C), and 77.39% oxygen (O) by mass?

                HCO (Insert subscripts as needed.)

9) A compound with the empirical formula CH2 has a molar mass of 98 g/mol. What is the molecular formula for this compound?

Answer 1

1)

moles of BaCl2 = 51.3 / 208.2 = 0.2464

1 mol contain -------------- 6.023 x 10^23 atoms

0.2464 mol contain ------------ ??

number of atoms = 0.2464 x 6.023 x 10^23 = 1.484 x 10^23

number of atoms =1.484 x 10^23

2)

moles of CO = 29.3 / 28 = 1.05

moles of CO = 1.05

3)

formula = Cu₃(PO₄)₂

4)

1 mol of copper(II) phosphate ----------- 2 atoms

2.90 mol Cu₃(PO₄)₂ ---------------- 2.90 x 2 x 6.023 x 10^23 = 3.493 x 10^24

number of atoms = 3.493 x 10^24

5)

moles of N2O = 0.191 / 44 = 4.341 x 10^-3

moles of N = 8.682 x 10^-3

6) A sample of C3H8 has 7.68 × 1024 H atoms. How many carbon atoms does the sample contain? What is the total mass of the sample?

moles = 7.68 x 10^24 / 6.023 x 10^24

          = 12.75

moles of H = 12.75

moles of C = 12.75 x 3 / 8 = 4.78

number of C atoms = 2.88 x 10^24

1 mol of C3H8 = 3 mol of C

?? mol C3H8 =    4.78 mol of C

mol of C3H8 = 1.593

mass of C3H8 = 1.593 x 44 = 70.1 g