# Moles Class Packet Unit 2

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• ### Potassium bicarbonate for baking

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Moles and Molar Mass

Find the gram formula mass of the following: (Show all work)

1. CO2

2. FeS

3. NaCl

4. Al2(CO3)3

5. SiO2

6. H2SO4

7. Al2(SO3)3

8. C12H22O4

9. Fe2O3

10. ZnCl2

11. Ca(OH)2

12. CH4

13. NH3

14. H2O2

15. NaHCO3

16. C6H12O6

17. MgO

18. SrSO4.3H2O

Find the number of moles in the following measurements: (Show your work)

1. 900. grams C6H12O6

2. 24.5 grams H2SO4

3. 192 grams SiO2

4. 450. grams of ZnCl2

5. 22 grams of CO2

6. 20. grams of Fe2O3

7. 3.40 grams of H2O2

8. 840. grams of NaHCO3

Now solve for the mass given the moles. (Show your work)

1. 2.00 moles of C6H12O6

2. 5.00 moles of SrSO4.3H2O

3. 0.250 moles of CH4

4. 0.100 moles of NH3

5. 12.0 moles of SiO2

6. 0.330 moles of FeS

7. 1.50 moles of MgO

8. 0.500 moles of ZnCl2

Molar Mass and Moles Regents Questions

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Honors Moles and Avogadro’s Number

Use dimensional analysis to convert the following:

1. A volume of 2.34x1025 molecules of oxygen gas to moles.

2. A volume of 5.56x1019molecules of carbon dioxide gas to moles.

3. A 0.365 mole sample of sulfur hexafluoride gas to molecules.

4. A 3.98 mole sample of nitrogen gas to molecules.

5. A sample of 5.67x1025 atoms of carbon to moles.

6. A sample of 1.09x1021 atoms of helium to moles.

7. A sample of 2.73 moles of nitrogen dioxide to molecules and atoms.

8. A sample of 0.0876 moles of bromine to molecules and atoms.

Coefficients and Moles

3Cu + 8HNO3 ( 3Cu(NO3)2 + 2NO + 4H2O

1. If 1.00 mole of water is produced, how many moles of HNO3 are used?

2. If 1.50 moles of copper are used, how many moles of NO are produced?

3. If 4.50 moles of HNO3 are used, how many moles of copper (II) nitrate are produced?

4. If 0.200 moles of NO are produced, what is the mass of copper (II) nitrate produced?

5. If 25.6 grams of HNO3 react, how many moles of H2O form?

Fe2O3 + 3CO ( 2Fe + 2CO2

6. If 3.00 moles of Iron (III) oxide are used, how many moles of Iron are formed?

7. If 2.50 moles of CO are used, how many moles of carbon dioxide are formed?

8. If 8.56 moles of iron were produced, how many moles of the iron ore were used?

9. If 25.68 grams of iron (III) oxide were used, how many grams of carbon dioxide are formed?

10. If 456g of Fe from, how many grams of iron(III) oxide were used?

Regents Questions

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Our Model so far…

Complete the table below using your knowledge of moles, molar mass, and mole ratios.

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Balancing Reactions

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Balance the reactions: Give the type of reaction:

1. NO + O2 ( NO2 _____________________________________________________

2. Ag + S ( Ag2S ____________________________________________________

3. Cu(OH)2 ( CuO + H2O ____________________________________________________

4. KClO3 ( KCl + O2 ____________________________________________________

5. Al + O2 ( Al2O3 ____________________________________________________

6. CO + O2 ( CO2 ____________________________________________________

Balancing Regents Questions

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Identify the type of reaction: Find the missing substance:

a. ___________ f. ___________

b. ___________ g. ___________

c. ___________ h. ___________

d. ___________ i. ___________

e. ___________ j. ___________

Multi-Step Dimensional Analysis

N2 + 3H2 ( 2NH3

1. Convert 5.68 grams of nitrogen to grams of ammonia gas at STP.

2. How many grams of hydrogen are formed from 45.67g of ammonia gas at STP?

3. How many molecules of hydrogen will react with 4.56x1024 molecules of nitrogen?

2H20 ( 2H2 + O2

4. How many grams of oxygen can be formed from 56.0 grams of water?

5. If 3.87x1025 molecules of water are used, how many grams of hydrogen gas form at STP?

6. If 34.5L of gaseous water are used, how many grams of hydrogen gas are formed at STP?

7. There is a short cut for conversions of molecules to molecules under the same conditions. Can you see it in question 3? Why isn’t there a similar short cut for mass to mass?

Limiting Reactants

Reactants are not always present in the exact amounts required by the balances chemical equation. In planning any cost effective production process, it is necessary to produce and use only what is needed, not have too much of any reactant left over, and to recognize which component limits the amount of material that can be produced.

Model: A cake recipe calls for: 2 cups of water 4 cups of sugar

4 cups of flour 8 oz of butter

8 squares of chocolate 4 eggs

Ingredients you have: lots of water 4 cups of sugar

5 cups of flour 16 oz of butter

12 square of chocolate 6 eggs

Key Questions:

1. According to the model, how much of each ingredient will you have left over after baking the cake?

|Water |Flour |Chocolate |Sugar |Butter |Eggs |

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2. Which ingredients were in excess?

3. Which ingredient was completely consumed?

4. What would be a good definition for the term limiting reactant?

5. Provide a good method for determining the limiting reactant and the final amount of the product before execution of the procedure.

Exercises:

6. You have 100 bolts, 150 nuts and 150 washers. You assemble a nut/bolt/washer set using the following equation: 2 washers + 1 bolt + 1 nut = 1 shell.

a. How many shells can you assemble from your supply?

b. What is the limiting component?

7. You react 150 H2 molecules with 100 O2 molecules to produce water.

a. Write the balance reaction for the synthesis of water.

b. Using your balanced equation, calculate which element is the limiter.

c. How many water molecules can be produced based on this supply?

d. If you had 1.73 moles of hydrogen and 0.89 moles of Oxygen, which is the limiter? How many moles of water can be produced?

e. If you had 17.3g of hydrogen and 8.91 g of oxygen, what is the limiting reactant and how many moles of water can be synthesized?

Limiting Reactants

For each word equation

• Write a balanced chemical equation

• Draw particulate representations of the reaction (make sure you include a key), make sure you include the correct number of each particle based on the information provided.

• Determine which reactant is limiting and which is in excess

1) Three molecules of oxygen react with four molecules of hydrogen to produce water molecules.

a. Balanced Chemical equation: _________________________________________

b. particulate representations of the reaction

c. Which reactant was limiting? _________ Excess? __________

2) Two sodium atoms react with three water molecules to produce sodium hydroxide and hydrogen gas.

a. Balanced Chemical equation: _________________________________________

b. particulate representations of the reaction

c. Which reactant was limiting? _________ Excess? __________

3) Four Aluminum atoms combine with three chlorine molecules to produce solid aluminum chloride.

a. Balanced Chemical equation: _________________________________________

b. particulate representations of the reaction

c. Which reactant was limiting? _________ Excess? __________

4) Two molecules of potassium chloride react with two molecules of silver oxide to produce potassium oxide and silver chloride

a. Balanced Chemical equation: _________________________________________

b. particulate representations of the reaction

Which reactant was limiting? _________ Excess? __________

5) Assuming the reaction goes to

completion , draw the resulting

particles in the box on the right.

Which reactant was limiting? ____

Our Model so far…

Complete the table below using your knowledge of balancing reactions, type of reactions, and limiting reactants.

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|Experimental: |Narrative: |

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Percent Composition

Determine the % composition of all elements in these compounds. Show all work!

1) sodium sulfide

Formula _______ Mass of Na _______ %Na _________

Molar mass _______ Mass of S _______ %S _________

2) aluminum phosphide

Formula _______ Mass of Al _______ %Al _________

Molar mass _______ Mass of P _______ %P _________

3) lithium bromide

Formula _______ Mass of Li _______ %Li _________

Molar mass _______ Mass of Br _______ %Br _________

4) calcium nitride

Formula _______ Mass of Ca _______ %Ca _________

Molar mass _______ Mass of N _______ %N _________

Empirical and Molecular Formulas

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Honors Empirical Formulas

1. A common oxide of nitrogen contains 25.93% N. Deduce the empirical formula of the oxide.

2. A compound that is usually used as a fertilizer can also be used as a powerful explosive. The compound has the composition 35.00% nitrogen, 59.96% oxygen and the remainder being hydrogen. What is its empirical formula? –

3. What are the empirical formulae for these compounds, that both contain five carbon atoms?

(a) C5H10

(b) C5H12

4. A substance has an empirical formula of CH2Br and a molar mass of 188 g mol-1. What is the molecular formula of the compound?

5. The common pain medicine, Advil, contains the active ingredient Ibuprofen that has a molar mass of 206 g mol-1. Ibuprofen contains 75.73% C, 8.74% H, the remainder being oxygen. What are the empirical and molecular formulae for Ibuprofen?

6. The molar mass of the common antibiotic oxytetracycline is found to be 460 g mol-1 and a 2.000 g sample contains 1.1478 g of carbon, 0.10435 g of H, 0.62609 g of oxygen and the remainder being nitrogen. What is the molecular formula of the oxytetracycline?

Our Model so far…

Complete the table below using your knowledge of percent composition, and empirical and molecular formulas.

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|Experimental: |Narrative: |

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Naming Binary Ionic Compounds

Ionic Compounds require two types of ions: cations which are positive and anions which are negative. All metals (on the left side of the periodic table) form cations and nonmetals (on the left side of the periodic table) form anions primarily. In order to determine the formula of the compound they create you must make sure their ions sum to zero. For example, table salt is sodium chloride. Using the periodic table’s first set of ions, sodium forms +1 ions and chlorine forms -1 ions. Therefore their ions cancel out and the formula is NaCl. It is not always that easy. Calcium chloride is the salt we put on roads to melt ice. Calcium forms +2 ions and Chloride forms -1 ions. We need two chloride ions to balance the charges. The formula is CaCl2. Notice the metal, or positive cation is always written first! Try the following examples:

1. Cesium fluoride: ______________ 4. Barium sulfide: ______________

2. Potassium oxide: ______________ 5. Aluminum chloride: ______________

3. Magnesium iodide: ______________ 6. Calcium phosphide: ______________

| |Chloride |Sulfide |Fluoride |Phosphide |

|Lithium | | | | |

|Aluminum | | | | |

|Magnesium | | | | |

|Potassium | | | | |

Now we know how to write formulas from their names but we also need to know how to write names from formulas. The rule is: write the whole name of the first element and the second element drop the ending and replace with “ide.” For example: H2S is hydrogen sulfide. In this case, the amount of each element doesn’t affect the name of the compound. Use table S to help you find names. Try to name the following examples:

1. NaF __________________________ 6. NaH ______________________________

2. MgCl2 __________________________ 7. K3P ______________________________

3. Al2O3 __________________________ 8. MgO ______________________________

4. MgI2 __________________________ 9. Li2Te ______________________________

5. H2O __________________________ 10. AlCl3 ______________________________

Naming with Transition Metals

Transition metals refer to the metals in groups 3-12 of the period table (elements Sc through Zn and down). These metals form various positive ions. It is important to identify which ion is used when naming the compound. We will work backwards to do this, meaning, we will look at the charge for the second ion in the formula to find that charge of the first. We will report the charge of the first ion in roman numerals (the numerals you need to memorize are listed to the right) in parenthesis after that ion. For example:

CuO O is -2 so Cu needs to be +2 Copper (II) oxide

Cu2O O is -2 so each Cu must be +1 Copper (I) oxide

These two compounds have different structures and properties and must have different names. Try to name the following compounds with transition metals:

1. FeBr2 ________________________ 6. NiF3 ________________________

2. FeBr3 ________________________ 7. CuCl ________________________

3. PbS ________________________ 8. CuCl2 ________________________

4. PbS2 ________________________ 9. CuS ________________________

5. NiO ________________________ 10. Cu2S ________________________

Formula writing may seem easier. You can still use the drop and swap rule. Remember the number in roman numerals refers to the charge of the first ion. Try to give the formula of the following compounds:

1. Chromium (VI) oxide _____________ 6. Zinc (II) oxide _____________

2. Manganese (VII) chloride _____________ 7. Iron (II) oxide _____________

3. Lead (IV) iodide _____________ 8. Iron(III) oxide _____________

4. Silver (I)sulfide _____________ 9. Gold (III) phosphide _____________

5. Nickel (II) fluoride _____________ 10. Titanium (IV) sulfide _____________

Naming with Polyatomic Ions

Binary compounds have only two elements in their formula, as we saw in exercises above. Tertiary compounds have three or more elements in their formula and have a new system of naming. These compounds have a polyatomic ion, which is an ion that has a few elements grouped together with only one charge between them. A common example is OH- which shows two elements with an overall charge of -1. As before, name the first element completely and then look up the rest of the compound on table E of the reference tables. Make sure you copy the right one, some are very similar! For example: NaOH is called sodium hydroxide. Also, beware of NH4+ which is the only polyatomic cation (that comes in front). Try naming the following examples:

1. KHCO3 _________________________ 4. LiNO2 ______________________________

2. CaSO4 _________________________ 5. Cu(ClO4)2 ______________________________

3. NaNO3 __________________________ 6. Al2(SO3)2 ______________________________

To write the formula of a tertiary compound you can still use the drop and swap rule, however, you must be sure to only drop the superscripts and leave the subscripts alone. For example, aluminum carbonate:

Al+3 and CO3-2 Leave the 3 alone! Swap the 3 and 2 Al2(CO3)3

Remember, formulas don’t show any charges. You can see that we use parenthesis around the polyatomic ion because the entire ion charge was -2 and must swap with aluminum so the entire ion gets aluminum’s 3. Try to write the formula for the following compounds (write the formulas of the ions next to the name first):

| |Hydroxide |Nitrate |Carbonate |Phosphate |Acetate |

|Sodium | | | | | |

|Calcium | | | | | |

|Ammonium | | | | | |

|Iron (II) | | | | | |

|Aluminum | | | | | |

Try a few more:

1. Zinc Hydroxide: ________________________ 4. Magnesium oxalate:______________________

2. Calcium chlorate: ________________________ 5. Lead (IV) chromate:_______________________

3. Hydrogen acetate: ________________________ 6. Stronium cyanide: ________________________

Review

| |Key Idea Question |Justify your answer |Confidence Level |

| | |with an explanation or calculation. | |

| | | |None Moderate |

| | | |Fully |

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|1 |What is the gram formula mass of Ca3(PO4)2? | | |

| |a. 279 g/mol c. 310 g/mol | |Pre-discussion: |

| |b. 87 g/mol d. 168 g/mol | | |

| | | |Post discussion: |

|2 |What is the empirical formula of N2O4? | | |

| |a. NO c. NO2 | |Pre-discussion: |

| |b. N2O4 d. NO3 | | |

| | | |Post discussion: |

|3 |What is a possible mass of a compound with the | | |

| |empirical formula CH4? | |Pre-discussion: |

| |a. 12 g/mol c. 24 g/mol | | |

| |b. 48 g/mol d. 20 g/mol | |Post discussion: |

|4 |According to the reaction, what is the ratio of | | |

| |hydrogen to oxygen? | |Pre-discussion: |

| |2H2 + O2 ( 2H2O | | |

| |2 mol:1 mol c. 2g : 1g | |Post discussion: |

| |1mol:2mol d. 1g: 2g | | |

|5 |What is the percent by mass of nitrogen in N2H4? | | |

| |44% c. 13% | |Pre-discussion: |

| |88% d. 78% | | |

| | | |Post discussion: |

|6 |Calculate the number of moles equal to 128.2 grams of | | |

| |P2O5. | |Pre-discussion: |

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| | | |Post discussion: |

|7 |Identify the types of reactions: | | |

| |N2 + O2 ( 2NO | |Pre-discussion: |

| |CuO2 ( Cu + O2 | | |

| |Ca(NO3)2 + 2Li ( 2LiNO3 + Ca | |Post discussion: |

| |2NaCl + Pb(NO3)2 ( NaNO3 + PbCl2 | | |

|8 |78 grams of K reacts with 60 grams of MgF2 and forms 58| | |

| |grams of potassium fluoride. How many grams of | |Pre-discussion: |

| |magnesium are formed? | | |

| | | |Post discussion: |

|9 |2.5 grams of a hydrate is heated to form 1.75 grams of | | |

| |the anhydrate. Calculate the mass of water in the | |Pre-discussion: |

| |original hydrate. | | |

| | | |Post discussion: |

|10 |Balance the reaction: | | |

| | | |Pre-discussion: |

| |___ N2 + ___ H2 ( ___NH3 | | |

| | | |Post discussion: |

Common Sense Chemistry Review

1. Scurvy is a condition many sailors had resulting in fatigue, skins spots, and loss of teeth due to lack of vitamin C. Your vitamin provides 35 milligrams of vitamin C per tablet. To prevent scurvy you need a daily dose of 65 milligrams. What percent (by mass) of vitamin C do you obtain from your vitamin?

2. A platinum ore site in Canada was discovered and everyone heads out to make some money. You obtain 8.25kg of platinum arsenide. Assuming you know how to extract the platinum and sell it, how much money can you make? PtAs2 ( Pt + 2As

a. What type of reaction will you carry out to extract the platinum?

b. Calculate the moles of PtAs2 recovered.

c. Calculate the moles of Pt formed.

d. Calculate the grams of Pt formed.

e. You get a buyer that will pay \$32 per gram. How much money will you make?

3. Your brother left his bike out in the back yard all winter and it has a red coating on it. What is the empirical formula and IUPAC name of the compound formed on the bike? Fe + O2 ( _________________

4. What type of reaction occurred in question 3?

5. You are asked to create acetaminophen, the main component for Tylenol, C8H9NO2. You follow procedures dutifully and weigh your final product. It weighs 453 g/mol. What is the molecular formula of the compound you’ve made? Is the product you formed safe to use in Tylenol?

6. The following are common names for compounds. Give the IUPAC name:

a. Baking soda NaHCO3

b. Bleach NaClO

c. Chalk CaCO3

d. Lime CaO

e. Water H2O

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One I Five V

Two II Six VI

Three III Seven VII

Four IV

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