1. WHITEBOARD PRACTICE TEST REVIEW

2. How many molecules of ethane, C 2 H 6 are present in 0.334 g C 2 H 6 ?

3. How many atoms of carbon are in the molecule above? 6 How many atoms of hydrogen are in the molecule above? 14 How many atoms of oxygen are in the molecule above? 1 What is the molar mass of the molecule above?102.18 g/mol

4. A tank is filled with 8 liters of methane gas, CH 4 at STP. How many molecules of methane are in the tank? Hint….Litersmolesmolecules 2 x 10 23 molecules of ethane

5. Calculate the percent composition by mass of carbon in menthol, C 10 H 20 O. Hint….Find molar mass of compound Mass of carbon / molar mass of compound 156.269 g 76.86% C

6. How many molecules of N 2 O 5 are present in 3.4 g of N 2 O 5 ? Hint….gramsmolesmolecules 1.9 x 10 22 molecules of N 2 O 5

7. If 3.907 g of carbon combines completely with 0.874 g of hydrogen to form a compound. What is the percent composition of carbon in this compound? Hint….Find total mass of C + H Mass of carbon / total mass 81.7% C

8. How many atoms of nitrogen are there in 36 grams of calcium nitrate, Ca(NO 3 ) 2 ? Hint…. grams moles atoms 2.6 x 10 23 atoms N Mole to mole ratio

9. Determine the number of grams of carbon found 85 g glucose, C 6 H 12 O 6. Hint….Find % C %C x 85 = 40% C 34 g C

10. A compound is found to contain 50.05 % sulfur and 49.95 % oxygen by weight. The molecular mass for this compound is 64.07 g/mol. What is the empirical formula for this compound? SO 2

11. Calculate the number of moles of glucose, C 6 H 12 O 6, present in 120 g of glucose. Hint….gramsmoles 0.67 mol glucose

12. What is the empirical formula of a 0.858 g sample of an unknown substance that is composed of 0.537 g of copper and 0.321 g of fluorine. Hint….Find moles CuF 2

13. NutraSweet is 57.14% C, 6.16% H, 9.52% N, and 27.18% O. The molar mass of NutraSweet is 294.30 g/mol What is the molecular formula of NutraSweet? Hint….Find empirical formula first C 14 H 18 N 2 O 5

14. What is the mass of 4.8 X 10 23 molecules of Fe(OH) 3 ? Hint…. grams moles molecules 86 g Fe(OH) 3

15. Calculate the percent composition of nitrogen in a 13.07 g sample of an unknown substance that is composed of 9.48 g of barium, 1.66 g of carbon, and 1.93 g of nitrogen. Hint….mass N / mass total 14.8% N

16. EXTRA PROBLEMS

17. From the formula for aluminum oxide, Al 2 O 3, calculate the mass of aluminum that can be obtained from 250 g of the compound.

18. Calculate the percent composition of a 0.858 g sample of an unknown substance that is composed of 0.537 g of copper and 0.321 g of fluorine.

19. A compound contains 57.54% C, 3.45% H, and 39.01% F. What is its empirical formula?

20. A compound is found to contain 31.42 % sulfur, 31.35 % oxygen, and 37.23 % fluorine by weight. The molecular weight for this compound is 102.2 g/mol. What is its molecular formula?

21. A 0.400 g sample of a white powder contains 0.141 g of potassium, 0.115 g of sulfur, and 0.144 g of oxygen. The molar mass of this compound is 86.1 g. What is the percent composition of sulfur?

22. Calculate the percent composition of a 13.07 g sample of an unknown substance that is composed of 9.48 g of barium, 1.66 g of carbon, and 1.93 g of nitrogen.

23. How many molecules of ethane, C 2 H 6 are present in 340 g C 2 H 6 ?

24. A compound contains 57.54% C, 3.45% H, and 39.01% F. What is its empirical formula?

25. Calculate the mass of chlorine in 85.0 g Mg(ClO 4 ) 2.

26. A compound is 19.3% Na, 26.9% S, and 53.8% O. Its molecular mass is 238 g/mol. What is the molecular formula?