Chemistry exam part 3!!!?

Question

1. Analysis of a compound found it to contain 15.77% Aluminum, 28.11% Sulfur and 56.12% Oxygen. What is it's empirical formula?

a. AlS2O6

b. Al2S3O12 or Al2(SO)4

c. AlSO4

d. Al2SO4

2. 3 moles of Sodium Hydroxide are added to 480 mL. of water. What is the mass percent of Sodium Hydroxide in this solution.

a. 33.3%

b. 25%

c. 7.5%

d. 20%

3. Aluminum when exposed to the air will combine with Oxygen to form Aluminum Oxide. If 108 g. of Aluminum is completely oxidized (reacted) how many moles of Aluminum Oxide will be produced?

a. 1

b. 2

c. 3

d. 4

4. In which type of reaction are the products always water and a salt?

a. Acid-Base

b. Precipitation

c. Combustion

d. Oxidation-Reduction

5. What type of bond is formed when Calcium combines with Oxygen to form Calcium Oxide?

a. Ionic

b. Polar Covalent

c. Covalent

6. Which element has the greatest reluctance to give up an electron? (Highest electronegativity)

a. Fracium

b. Hydrogen

c. Oxygen

d. Flourine

Answer 1

1. Analysis of a compound found it to contain 15.77% Aluminum, 28.11% Sulfur and 56.12% Oxygen. What is it's empirical formula?

Al 15.77g @ 27g/mol = 0.58 moles... / 0.58 = 1

S  28.11 g @ 32g/mol = 0.88 moles ../ 0.58 = 1.5

O 56.12 g @ 16 g/mol = 3.5 moles..../ 0.58 = 6

b. Al2S3O12 or Al2(SO4)3

(your answer "B" had a misprint, the (SO)4 's "4" belongs inside, & a "3" belongs outside, this allows it to equate to the "Al2S3O12")

2. 3 moles of Sodium Hydroxide are added to 480 mL. of water. What is the mass percent of Sodium Hydroxide in this solution.  3 moles NaOH = 120 grams

120g / 600 g = 20%

d. 20%

3. Aluminum when exposed to the air will combine with Oxygen to form Aluminum Oxide. If 108 g. of Aluminum is completely oxidized (reacted) how many moles of Aluminum Oxide will be produced?

  108 g Al  @ 1mole  Al2O3 / 54 g Al = 2 moles

b. 2

4. In which type of reaction are the products always water and a salt?

a. Acid-Base

5. What type of bond is formed when Calcium combines with Oxygen to form Calcium Oxide?

a. Ionic

6. Which element has the greatest reluctance to give up an electron? (Highest electronegativity)

d. Fluorine

Answer 2

In the first question the correct formula is Al2(SO4)3