2. The U.S. Food and Drug Administration recommends that you consume less than 2

Question

2. The U.S. Food and Drug Administration recommends that you consume less than 2.4g of sodium per day. What mass of sodium chloride (in grams) can you consume and still be within the FDA guidelines? First determine the % by mass of sodium in sodium chloride.

Empirical and Molecular Formulas

3. A compound containing nitrogen and oxygen decomposed in the laboratory and produces 24.5 g nitrogen and 70.0 g oxygen. Calculate the empirical formula of the compound.

4. A laboratory analysis of aspirin determined the following mass percent composition:

Carbon 60.00%; Hydrogen 4.48%; Oxygen 35.52%. Find its empirical formula.

5. Butanedione is a main component in the smell and taste of butter and cheese. It is made up of carbon, hydrogen and oxygen. Its empirical formulas is C2H3O and its molecular mass is 86.09g per mol, determine its true (molecular) formula.

6. Upon combustion, a 0.8233g sample of a compound containing carbon, hydrogen and oxygen produced 2.445g CO2 and 0.6003g H2O.

            a. How many moles of CO2 are there in 2.445g CO2?

b. How many moles of C in 2.445 g CO2?

c. How many moles of water are there in 0.6003g of water?

            d. How many moles of hydrogen are there in 0.6003g H2O?

            e. What are the total moles of oxygen from the CO2 and H2O?

How many molecules of CO2 are there in 2.445 g CO2?

Equations and mole-to-mole relationships

7. The concepts of Stoichiometry are familiar to those who cook in the kitchen. For example, suppose the recipe for pizza is:

1 crust + 5 oz tomato sauce + 2 cups cheese à 1 pizza

This recipe shows the numerical relationships between the pizza ingredients. Show your calculations for determining the number of pizzas you could make if you have 6 cups of cheese and enough of the other ingredients.

8. For the following reaction:

4Cr(s) + 3O2(g) à 2Cr2O3(s)

Starting with 10.4g of O2, how many moles of Cr2O3 can be produced:

How many grams of Cr metal would be needed to fully react with 10.4g oxygen?

9. Sulfuric acid (H2SO4) is a component of acid rain which forms when SO2, a pollutant, reacts with oxygen and water in the atmosphere according to the following equation:

2SO2(g) + O2(g) + 2 H2O(l) à 2H2SO4(aq)

If the electricity generation plant produces 25 kg of SO2 per year to provide electricity for your house, calculate the kg of H2SO4 which can form.

Explanation / Answer

2. For 2.4 g of Na,

NaCl needed = (2.4 g/23 g/mol) x 58.44 g/mol = 6.10 g

mass% = Na/NaCl = (2.4 x 100/6.10) = 39.34%

3. moles of N = 24.5/14 = 1.7

moles of O = 70/16 = 4.4

divide by smallest factor

N = 1.7/1.7 = 1

O = 4.4/1.7 = 2.5

Empirical formula of compound = N2O5

4. moles of C = 60/12 = 5

moles of H = 4.48/1 = 4.48

moles of O = 35.52/16 = 2.22

divide by smallest factor

C = 5/2.22 = 2.25

H = 4.48/2.22 = 2

O = 2.22/2.22 = 1

Empirical formula of compound = C7H6O3

5. ratio = molecular mass/empirical formula mass = 86.09/(2x12 + 3x1 + 16) = 2

Molecular formula of butanedione = C4H6O2

6. a. moles of CO2 = 2.445/44 = 0.055 mols

b. moles of C = 0.055 mols

c. moles of H2O = 0.6003/18 = 0.033 mols

d. moles of hydrogen = 0.067 mols

e. total moles of oxygen from CO2 and H2O = 2 x 0.055 + 0.033 = 0.143 mols

f. molecules in 2.445 g CO2 = 0.055 x 6.02 x 10^23 = 3.311 x 10^22 molecules

7. 2 cups cheeze used for making 1 pizza

So 6 cups cheeze would be used for = 6/2 = 3 pizza

8. moles of O2 = 10.4/32 = 0.325 mols

moles of Cr2O3 formed = 0.325 x 2/3 = 0.22 mols

mass of Cr2O3 formed = 0.22 x 151.99 = 33.44 g

with, 10.4 g O2, Cr needed = 0.325 x 4/3 = 0.433 mols

mass of Cr metal needed = 0.433 x 52 = 22.52 g

9. moles of SO2 = 25/64.066 = 0.39 kmols

mass of H2SO4 formed = 0.39 x 98.079 = 38.25 kg

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.