# mole and Avogadro's Number

Please see the attached file for the complete problems.

"Activity - Stoichiometry Exercises"

1. 1a. How many atoms are in 12 molecules of glucose.

1a. How many atoms are in 12 molecules of glucose, C6H12O6 ?

Use exact value for this answer.

24

2. 1b. How many moles of fluorine gas (F<sub>2</sub> molecule)?

1b. How many moles of fluorine gas (F2 molecule) are present in 55.0 grams of fluorine (F2) ?

Use three significant figues and express your answer.

1.45

3. 1c. What is the mass (g) of a single molecule of CO<sub>2</sub>

1c. What is the mass (g) of a single molecule of CO2 ? Hint: Express your answer in terms of grams per molecule.

Use three significant figues and express your answer in exponential notation.

0.0000000000249 = 2.49 e -11

1.

4. 1d. What is the atomic mass (atomic weight, g/mol) of an element.

1d. What is the atomic mass (atomic weight, g/mol) of an element that weighs 9.12 x 10-23 g ?

Round off your answer to the tenth of a gram/mole.

1.

5. 1e. Mole and Avogadro's Number: C8H9O4

01e. What is the mass (grams) of 0.216 mol of C8H9O 4 ?

Round off to the tenth of a gram.

1.

6. 2a. Balancing Equation and the Mole Concept

2a. Balance the equation and determine the number of moles of potassium chlorate (KClO3) required if 6 moles of potassium chloride and 9 of oxygen is produced from its decomposition.

Type in the moles of potassium chlorate.

Your answer should be an exact number.

1.

7. 2b. Balancing Equation and the Mole Concept

2b. How many moles of H2O will be produced from the complete combustion of 4.4g of C3H8 ?

Round off your answer to the hundredth of a mole.

1.

8. 2c. Balancing Equation and the Mole Concept

2c. A sample of ammonium dichromate (NH4)2Cr2O7, contains 2.25 mol of hydrogen atoms. What is the number of moles of oxygen atom in the sample?

Round off your answer to the tenth of a mole.

1.

9. 2d. Balancing Equation and the Mole Concept

2d. Balance the equation and determine the mass (grams) of nitrogen dioxide produce when 102.0 grams of ammonia reacts with excess oxygen to produce nitrogen dioxide and water.

Round off your answer to a tenth of a gram.

1.

10. 3a. Mass of hydrogen

3a. Calculate the mass (grams) of hydrogen formed when 25.00 g of aluminum reacts with excess HCl. The other product from this reaction is aluminum chloride.

Use four significant figures in your final answer.

1.

11. 3b. Mass of ammonia

3b. Carbon dioxide, CO2, and ammonia, NH3, combines together to form urea, CH4N2O, plus water. Write a balanced equation and calculate the mass of ammonia in grams that would be needed to make 2.0 moles of urea.

Use two significant figures.

1.

12. 3c. Grams of oxygen

3c. How many grams of oxygen are required to burn the 14.4 g of C5 H12 ?

Round off your answer to the tenth of a gram.

1.

13. 3d. Moles of oxygen

3d. How many moles of oxygen are needed to produce 11.0 g of P4 O6 from phosphorus

Round off to a thousandth of a mole.

1.

14. 3e. Percent yield of Iron.

3e. What is the percent yield for a reaction when 6.50 grams of Fe2 O3 combines with carbon monoxide to produce 3.85 g of iron ? (not balanced) __Fe2O3 + __CO ---> __Fe + CO2

Round off your answer to a tenth of a percent.

1.

15. 3f. Molecules of nitrogen dioxide.

3f. How many molecules of nitrogen monoxide is produced if 92.0 g of nitrogen dioxide is combine with excess water according to the following reaction? (Not balanced) __NO2(g) + __H2O(l)  __HNO3(g) + __NO(g)

Use three significant figues and express your answer in exponential notation.

2350 = 2.35 e + 03

1.

https://brainmass.com/chemistry/composition-stoichiometry/mole-and-avogadro-s-number-207781

#### Solution Summary

The solutoin works on questions dealing with mole and Avogadro's Number.

Lab on Avogadros Law

1. Take a gas piston from the Glassware shelf and place it on the workbench. The gas piston is like a syringe, except that the piston/plunger is free to move up and down in order to equalize the pressure of its contents with the outside room pressure.

2. Take a balance from the Tools shelf and drop it on the gas piston. Record the mass of the empty gas piston.

3. Select a gas from the Chemicals shelf and fill the gas piston with 100 mL of the gas. Weigh the gas piston and gas and record the total mass.

4. Take four more gas pistons from the Glassware shelf and fill them each with 100 mL of one of the other four gases on the Chemicals shelf.

5. Weigh and record the total masses of each piston with gas.

6. Open the Data window and click on each gas piston. Record the molecular weight (MW) of each gas.

Questions

1. Record the mass of the empty gas piston (g):

2. For each gas, record the following:

(a) Name and formula

(b) Mass of gas piston and 100 mL gas (g)

(c) Mass of 100 mL gas (g)

(d) Molecular weight of the gas (g/mole)

(e) Number of moles in the 100 mL sample

% deviation = |(moles of gas) - (average for all gases)| / (average for all gases) * 100%

(a) Average number of moles in 100 mL for all five gases:

(b) % deviation for each gas:

(c) Do your results confirm Avogadro's Law?

4. Volume occupied by one mole of gas at STP. One mole of any gas at STP conditions (standard temperature and pressure) occupies 22.4 liters. See how well the average number of moles for the gases agrees with this.

(a) Calculate the volume occupied by one mole of gas from the average number of moles in the 100 mL volume using the following proportionality equation:

average moles / 100 mL = 1 mole / (volume of 1 mole)

(b) You should get something close to 22.4 L. This number must then be corrected for non-STP conditions in the lab as follows. Click on the wall chart at the top of the lab (just under the lab title) to view the current temperature and pressure in the room. For ideal gases, PV/T is constant, and at STP, P=1 atm, V=22.4L, T=273.15K (0C). Solve for the corrected volume at the lab temperature and pressure. Recalculate the expected moles in the corrected volume at lab temperature and pressure. Report your experimental results using the corrected volume for 1 mole of gas, along with the percent deviation.

(c) Explain what might have caused your value to differ from the accepted value.

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