9. Find the mass in grams. a. 4.30*10^16 atoms He, 4.00 g/mol b. 5.710*10^23 mol

Question

9. Find the mass in grams. a. 4.30*10^16 atoms He, 4.00 g/mol b. 5.710*10^23 molecules CH4, 16.05 g/mol c. 3.012*10^24 ions Ca^2+, 40.08 g/mol 10. Find the number of molecules or ions. 11. What is the mass of 6.022*10^23 molecules of ibuprofen (molar mass of 206.31 g/mol)? 12. Find the mass in grams. 13. Find the number of molecules. 14. Why do we use carbon-12 rather than ordinary carbon as the basis for the mole? 15. Use skills Toolkit 1 to explain how a number of atoms is converted into amount in moles.

Explanation / Answer

9

(1) 4.30 x 1016 atoms

6.023 x 1023 atoms of He = 4.0 g/mol

4.30 x 1016 atoms of He = 4.0 x 4.30 x 1016 /6.023 x 1023= 2.855 x 10-7 g

(2) 5.710 x 1023 molecules

6.023 x 1023 molecules of CH4 = 16.05 g/mol

5.710 x 1023 molecules of CH4 = 16.05 x 5.710 x 1023 /6.023 x 1023 = 15.216 g

(3) 3.012 x 1024 ions

6.023 x 1023 ions of Ca2+ = 40.08 g/mol

3.012 x 1024 ions of Ca2+ = 40.08 x 3.012 x 1024 /6.023 x 1023 = 20.04 x 10 = 200.4 g

10) (a) 1.000 g of I-

126.90 g of I- = 6.023 x 1023 ions

1.000g of I- = 6.023 x 1023/1.000 = 6.023 x 1023 ions

(b) 3.5 g of Cu2+

63.55 g of Cu2+ = 6.023 x 1023 ions

3.5 g of Cu2+ = 3.5 x 6.023 x 1023/ 63.55 = 0.332 x 1023 ions

(c) 4.22 g of SO2

64.07 g of SO2 = 6.023 x 1023 molecules

4.22 g of SO2 = 4.22 x 6.023 x 1023 /64.07 = 0.397 x 1023molecules

11) 6.022 x 1023 molecules of ibuprofen

6.022 x 1023 molcules = 206.31 g of ibuprofen

12) mass in grams

(a) 4.01 x 1023 atoms of Ca

6.023 x 1023 atoms of Ca = 40.08 g

4.01 x 1023 atoms of Ca = 40.08 x 4.01 x 1023 /6.023 x 1023 = 26.68 g

(b) 4.5 mol of boron

1mole of Boron = 6.023 x 1023 = 11.01 g

4.5 mole of boron = 4.5 x 11.01 = 49.545 g

(c) Its not visible from the image

13) Mass of molecules and number of molecules

(a) 2.0 mol H2

1 mole of H2 = 2.0 g

2 moles = 2.0 x 2 = 4.0 g

1 mole of H2 = 6.023 x 1023 molecules

2 mole sof H2 = 2 x 6.023 x 1023 molecules = 12.046 molecules

(b) 4.01 g of HF

1 mole of HF = 20.01 g

20.01 g of HF = 1 mole

4.01 g of HF = 1 x 4.01/20.01 = 0.200 mole of HF

1 mole of HF = 6.023 x 1023 molecules

0.200 mole of HF = 0.200 x 6.023 x 1023 molecules = 1.207 x 1023 molecules

(c) 4.5 mol of C6H12O6

180.18 g 0f C6H12O6 =1 mole of C6H12O6

1 mole of C6H12O6 = 6.023 x 1023 molecules

4.5 mole of C6H12O6 = 4.5 x 6.023 x 1023 molecules = 27.1035 x 1023 molecules

14) We use C-12 as basis for the mole because it is the standard for the formal definition of the mole. According to the definition, one mole of carbon-12 has a mass of exactly 12 grams. Consequently, the molar mass of carbon-12 is 12 g/mol

15 )

1 mole of compound = 6.02 x1023 molecules

1 mole of atom = (6.022 x 1023 ) atoms

1 atom = 1/6.022 x 1023 mole

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