Name: ________________________________ Date:________ Per:__Chapter 12: Stoichiometry - https://youtu.be/XnfATaoubzA

https://youtu.be/S6UQX7ZdkTg

Stoichiometry: From the Greek, meaning “measuring elements”Measuring substances that go into and come out of chemical reactionsAllows us to count atoms and molecules by determining their mass

Review of old concepts from the mole chapter for this chart: Do you remember the conversion factors we used? Fill in the missing information in this table:

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Covalent moleculesIonic compounds Ions that would be found in an ionic

crystal

Mass Mole Particles Mole1 mole O2

32.00 g O2

1 mole O2

___________ molecules O2

1 mole CO2

_________g CO2

1 mole He6.02 x 1023 _______of He

______g He1 mole He

6.02 x 1023 ____________ NaCl1 mole NaCl

________g C6H12O6

1 mole C6H12O6

6.02 x 1023 Br- ions1 mole ___________

STOICHIOMETRY: MOLE-MOLE PROBLEMS

Stoichiometry Step-by-Step!

Ex. How many moles of O2 are needed to react with 0.52 moles of Mg?

Step 1 Balance the equation

2 Mg + 1 O2 2 MgO

Step 2 Write the given mole quantity (start your bridge)

Step 3 Write the mole ratio (moles of what you want / moles of what you have) (This comes from step 1a -the coefficients in the balanced equation)

Guided Practice with Mole-Mole Problems: http://youtu.be/S6UQX7ZdkTg 2

Mole –Mole is one step!1. Balance the equation: _1__ N2 + __3_H2 __2NH3

How many moles of hydrogen are needed to completely react with 2 moles of nitrogen?

2. Balance the equation: _____KClO3 _____KCl + _____O2

How many moles of oxygen are produced by decomposition of 6 moles of potassium chlorate?

3. Balance the equation: _____Zn + _____ HCl _____ZnCl2 + _____H2

How many moles of hydrogen are produced from the reaction of 3 moles of zinc with an excess of hydrochloric acid?

4. Balance the equation: ____C3H8 + ____O2 ____CO2 + _____H2O

How many moles of oxygen are necessary to react completely with 4 moles of propane (C3H8)?

5. Balance the equation: ______K3PO4 + _____Al(NO3)3 ____KNO3 + ____AlPO4

How many moles of potassium nitrate are produced when 2 moles of aluminum nitrate react?

STOICHIOMETRY: MASS-MASS PROBLEMSGiven the mass of one substance and asked to find the mass of another substance in a RXN gram A mole A mole B gram B

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6 mol H2

2 mol N2 3 mole H2

1 mole N2

Use coefficients from balanced equation

Add up the grams for only one mole of KCl. Ignore the coefficient here

Add up the grams for only one mole of KClO3. Ignore the coefficient here.

Just use the mass for only one mole of Al. Ignore the coefficient here.

Add up the grams for only one mole of Al2O3. Ignore the coefficient here.

5.0 grams ? grams

? grams5.0 grams

25.0 grams

Add up the grams for only one mole of KClO3. Ignore the coefficient here.

? grams

given g A 1 mole A coef mole B MM g B MM g A coeff mole A 1 mole B

Ex. 2.30 g of aluminum reacts with iron (III) oxide to form aluminum oxide and iron. How much aluminum oxide will be produced?

2Al + Fe2O3 1Al2O3 + 2Fe

Guided Practice with Mass – Mass Poblems:

1. Given the balanced equation: 2 KClO3 2 KCl + 3O2

How many grams of potassium chloride are produced if 25.0 g of potassium chlorate decompose?

25.0g KClO3 mole KClO3 mol KCl MM g KCl MMg KClO3 mol KClO3 mole KCl

2. Given the balanced equation: N2 + 3H2 2NH3

How many grams of hydrogen are necessary to react completely with 50.0 g of nitrogen in the above reaction?

50.0g N2

3. Use the 50.0 g of nitrogen to calculate how many grams of ammonia (NH3) are produced in the reaction in Problem 2?

4. Given the balanced equation:

2AgNO3 + BaCl2 2AgCl + Ba(NO3)2

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15.2g KCl

1st : Fill in ONLY YOUR UNITS.2nd : add the numbers.

gram Amole A mole B gram B

How many grams of silver chloride are produced from 5.0 g of silver nitrate reacting with an excess of barium chloride?

5. Use the 5.0 g of silver nitrate to calculate how much barium chloride reacts in the last problem.

STOICHIOMETRY: MIXED GUIDED PRACTICE PROBLEMS

1. When iron is heated in pure oxygen, iron (III) oxide is formed. Write a balanced equation for the reaction below. What type of reaction is it? __________________________________

Equation:______________________________________________________________________

a. What mass of iron must react with excess oxygen in order to form 4.81 moles of iron(III) oxide?

b. What mass of iron is needed to react with 40.0 g of oxygen?

c. What mass of iron(III) oxide can be formed from the reaction of 10.2 g of iron with excess oxygen?

d. What mass of oxygen is needed to react with 12.7 g of iron?

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2. Barium hydroxide reacts with hydrochloric acid (HCl) to form barium chloride and water. Write a balanced equation for the reaction below. What type is it? ____________________

_________________________________________________________________________________

a. What mass of barium chloride will form if 14.0 g of barium hydroxide reacts with excess hydrochloric acid?

b. How many grams of hydrochloric acid are needed to react with 15.0 g of barium hydroxide?

c. What mass of barium chloride will form if 5.98 g of hydrochloric acid react with excess barium hydroxide?

d. How many molecules of water are formed by the reaction of 10.8 g of barium hydroxide with excess hydrochloric acid?

LIMITING REACTANTS Which reactant limits the amount of product? https://youtu.be/c11YBShZnmA

http://youtu.be/qL_l8LA6

4.00 grams ?

Scenario:

You have 9 pieces of salami and 22 pieces of bread. EACH SANDWICH TAKES 1 PIECE OF SALAMI. What is the maximum amount of sandwiches you can make?_______

Question: Which limited us to the # of sandwiches? salami or bread The same thing happens in a chemical reaction. If information about BOTH of the reactants is given, it is your job to figure out which reactant was the one which limited the amount of product (we call this the limiting reactant – which is always used up) and which reactant was in excess and is not used up.

Example:2.00 grams of NH3 reacts with 4.00 grams of O2. Determine which reactant was the limiting reactant and how much NO was produced. The other product is H2O.

Balanced reaction: 4NH3 + 5O2 4NO + 6H2O

To Solve:

Step 1: Use stoichiometry to convert each reactant to the same product. You will usually be directed to a particular product but if not, you may choose which product you want to find. Step 2: Compare the amounts of each product produced. The smaller answer is the real answer. The larger amount must be crossed out since it actually never existed.

Step 3: The reactant which made the smaller amount of product is the limiting reactant.

Step 4: The other one is the excess reactant.

Final answer: O2 was the limiting reactant (LR) (which runs out ) and 3.00 grams of NO is produced. NH3 was the excess reactant(ER)

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LR

Real amount of product produced

ER

20.0 grams 15.0 liters

28.0 grams 25.0 grams

?

Guided Practice Limiting Reactant Problems

1. Predict the mass of aluminum oxide that will form if 20.0g of aluminum react with 15.0L of oxygen gas at STP. Write a balanced equation for the reaction below and then solve.

RXN: _________4Al + 3O2 2Al2O3___________________________

Identify the limiting reactant (LR): ____Al____Identify the excess reactant(ER): ____ O2___

Guided Practice: Limiting Reactant Problems

1. Given the balanced equation: N2 + 3H2 2NH3

How many grams of NH3 can be produced from the reaction of 28 g of N2 and 25 g of H2?

2. Given the balanced equation: Mg + 2HCl MgCl2 + H2

What volume of hydrogen at STP is produced from the reaction of 50.0 g of Mg and 75 g of HCl?

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(one reactant)

20.0g Al x 1 mole Al x 2 moles Al2O3 x 101.96g Al2O3= 37.8g Al2O3

26.98gAl 4 mole Al 1 mole Al2O3

15.0L O2 x 1 mole O2 x 2 moles Al2O3 x 101.96g Al2O3= 45.5g Al2O3

22.4L O2 3 mole O2 1 mole Al2O3

(one reactant)LR

(other reactant)ER (Excess Reactant)

3. Given the balanced equation: 3AgNO3 + Na3PO4 Ag3PO4 + 3NaNO3

Silver nitrate and sodium phosphate are reacted in equal amounts of 200 g each. How many grams of silver phosphate are produced?

4. Fluorine gas is bubbled through a solution of potassium iodide. The products of the reaction are potassium fluoride and iodine. Write a balanced equation for the reaction below and then answer the questions.

RXN: _________________________________________________________

a. What type of reaction is this? ____________________________

b. 1.26g of fluorine are bubbled through a solution containing 20.15g of potassium iodide. What mass of potassium fluoride should form?

c. Identify the limiting reactant: _______________

d. Identify the excess reactant: _______________

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HOW DO YOU FIND THE MASS OF LEFT OVER EXCESS REACTANT (knowing that the limiting reactant runs out!!!!)

Stop at 2:29 and RESTART at 4:25 https://www.youtube.com/watch?v=0ovs9laEibg

Maybe no…..http://youtu.be/0ovs9laEibgSteps to find the amount of EXCESS reactant REMAINING:

1) 1st find which reactant is the LR (limiting reactant) and which is the reactant in excess. (Bring each reactant to product and the reactant which yields the smaller amount of product is the LR)

2) To calculate the amount of excess reactant USED: Start a bridge from LR to the excess reactant (ER).

3) Subtract the answer from #2 from the amount of the excess reactant originally given to find out how much is left over.

Example: 90.0g of Iron(III) chloride reacts with 52.0g of hydrosulfuric acid to produce hydrochloric acid and Iron(III)sulfide. Find the limiting reactant, the amount of hydrochloric acid produced and the amount of excess reactant.

Start with the LR to find the ER that was used up in the reaction. (LRER) Then we can subtract.

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LR + Excess products

Grams of excess reactant that you BEGAN with MINUSGrams of excess reactant that you use (reacted) Grams of excess reactant (left over) (wasted)

2FeCl3 + 3H2S 6HCl + Fe2S3

We had 22 pieces of bread but only used 6 pieces so 22 (have) – 6 (used)= 16 pieces in excess

90.0 FeCl3 x 1 mole FeCl3 x 3 mole H 2S x 34.1g H2S = 28.4gH2S reacted 162gFeCl3 2 mole FeCl3 1 mole H2S

90.0 FeCl3 x 1 mole FeCl3 x 6 mole HCl x 36.5gHCl= 60.8g HCl 162gFeCl3 2 mole FeCl3 1 mole HCl

52.0g H2S x 1 mole H2S x 6 mole HCl x 36.5gHCl= 111 g HCl 34.1g H2S 3 mole FeCl3 1 mole HCl

52.0g H2S – 28.4g = 23.6g excess

LR

ER

Subtract what you started with minus what the reaction used!

Example: If 46.7 grams of iron(II) carbonate react with 65.0 grams of barium chloride, what mass of excess reactant remains?

FeCO3 + BaCl2 FeCl2 + BaCO3

Start with the LR to find the ER that was used up in the reaction. Then we can subtract.

The next step in the limiting reactant process is determining the amount of excess reactant

Try the problem below:

1. What mass of carbon dioxide will be formed if 50.0g of propane gas (C3H8) are burned in 40L of pure oxygen at STP?

a. Balanced Reaction: ___________________________________________________________

b. Find out which reactant is limiting and which reactant is excess.

c. The limiting reactant is ________________. The excess reactant is ________________.

d. Use the limiting reactant to determine how much of the excess reactant does react.

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46.7g FeCO3 x 1 mole FeCO3 x 1 mole FeCl 2 x 126.75gFeCl2= 51.1g FeCl2 so FeCO3 is ER 115.86gFeCO3 1 mole FeCO3 1 mole FeCl2

65.0g BaCl2 x 1 mole BaCl2 x 1 mole FeCl 2 x 126.75gFeCl2= 39.6g FeCl2 so BaCl2 is LR 208.23g BaCl2 1 mole BaCl2 1 mole FeCl2

65.0g BaCl2 x 1 mole BaCl2 x 1 mole FeCO 3 x 115.86gFeCO3 = 36.2gFeCO 3 used 208.23g BaCl2 1 mole BaCl2 1 mole FeCO3

46.7 g FeCO3 started with - 36.2gFeCO3 used = 10.5 g are in excess- left over!!!!!!!!!!!!!!!!!!!!!!!!!!!!

e. Subtract the amount that reacts from the amount you started with to find the mass remaining.

SAMPLE PROBLEM: FINDING THE MASS OF EXCESS REACTANT

35.0g of copper reacts with 90.0g of silver iodide What mass of copper(II) iodide will be formed?

a. Balanced Reaction: ______________________________________________________

b. Find out which reactant is limiting and which reactant is excess.

c. The limiting reactant is ____________. The excess reactant is __________.

d. Use the limiting reactant to determine how much of the excess reactant does react. (LRER)

e. Subtract the amount that reacts from the amount you started with to find the mass remaining.

PERCENT YIELDhttps://youtu.be/L7NEeVY4-P0

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https://youtu.be/tr9ijLSoMV4

(How well did you do in the lab?)

If you calculated a 3% error in a lab, then you should have a 97% yield. If you calculated a 10% error in a lab, then you should have a 90% yield.

Percent Yield: a comparison of how much product you produced in the lab and what you theoretically should have made according to your calculations.

Example (simplified)When “X” and “Y” react, stoichiometry shows that 51.0g of “Z” should be made but in the lab, you only produced 30.5g of “Z”. Find the % yield. Answer: (30.5/51.0 ) x 100 = 59.8%

Guided Practice Percent Yield:

1. Determine the percent yield for the reaction between 3.74 g of Na and enough O2 produces 3.00 g of Na2O(product) in the lab. 4 Na + O2 2Na2O3.74g Na 1 mole Na 2 mol Na2O 61.95 g Na2O = 5.04g Na2O

22.98gNa 4 mol Na 1 mole Na2O

3.00g x 100 = 59.52% 5.04

2. Determine the percent yield for the reaction between 6.92 g of K and enough O2 if 7.36 g of K2O (product) is produced in the lab. 4 K + O2 2K2O

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What you actually produced in lab

What stoichiometry predicts you will produce.

LAB

STOICH What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.What stoichiometry predicts you will produce.

3. Determine the percent yield for the reaction between 45.9 g of NaBr and excess chlorine gas to produce 12.8 g of NaCl and an unknown quantity of bromine gas.

4. Determine the percent yield for the reaction between 15.8 g of NH3 and excess oxygen to produce 21.8 g of NO gas and water.

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HW #1: MOLE-MOLE PROBLEMS

1. How many moles of ammonia are made if you start with 5.8 moles of hydrogen?

____N2 + ____ H2 ____ NH3

_______________

2. How many moles of potassium chloride are produced if you start with 3.45 moles of potassium chlorate?

____KClO3 ____ KCl + ____ O2

________________

3. How many moles of hydrochloric acid are needed to produce 6.17 moles of zinc chloride?

____Zn + ____HCl____ZnCl2 + ____H2

________________

4. How many moles of water vapor are produced from 13.8 moles of propane?

____C3H8 + ____ O2 ____ CO2 + ____ H2O

________________

5. How many moles of aluminum nitrate are needed to make 9.7 moles of aluminum phosphate?

____K3PO4 + ____Al(NO3)3 ____ KNO3 + ____AlPO4

________________

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HW #2: STOICHIOMETRY MASS-MASS

1. How many grams of potassium chloride are produced in 25 g of potassium chlorate decompose?

____ KClO3 ____ KCl + ____ O2

2. How many grams of hydrogen are necessary to react completely with 50.0 g of nitrogen in the following reaction?

____N2 + ____ H2 ____ NH3

3. How many grams of ammonia are produced in the reaction in problem 2?

4. How many grams of silver chloride are produced from 5.0 g of silver nitrate reacting with an excess of barium chloride?

____ AgNO3 + ____BaCl2 ____ AgCl + ____Ba(NO3)2

5. How much barium chloride is necessary to react with the silver nitrate in problem 4?

HW #3: MOLE/MASS PROBLEMS

When aluminum carbonate decomposes, aluminum oxide and carbon dioxide gas form.The reaction is given below:

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____Al2(CO3)3(s)____ Al2O3(s) + ____ CO2(g)

a. Determine the molar mass of each product and reactant for later use:

Al2(CO3)3

Al2O3

CO

b. What mass of aluminum carbonate is needed to form 2.5moles of carbon dioxide?

________________

c. What mass of aluminum oxide will form if 2.2moles of carbon dioxide form?

________________

d. What mass of aluminum carbonate must decompose in order to form 2.2 moles of aluminum oxide?

________________

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HW #4: MOLE-MOLE/MASS MIXED PROBLEMS

When fluorine gas is bubbled through a solution of aluminum iodide, iodine and aluminum fluoride are formed. Write and balance the reaction below:

RXN:

1. How many moles of fluorine gas are needed to react with 2.50 moles of aluminum iodide?

________________

2. What mass of iodine will form if 4.20 moles of fluorine gas react with excess aluminum iodide?

________________

3. What mass of fluorine gas is needed to react with 2.15moles of aluminum iodide?

________________

4. How many moles of aluminum fluoride will be produced if 20.0g of fluorine react with excess aluminum iodide?

________________

HW #5: LIMITING REACTANT AND % YIELD18

1. Solid calcium is added to a solution of iron(III) chloride. The reaction is given below:

____Ca + ____FeCl3 _____ CaCl2 + ____Fe

a. Balance the reaction.b. What mass of calcium chloride will form if 5.0g of calcium react with 5.0g of iron(III) chloride?

_______________

c. The limiting reactant is: _______________________d. The excess reactant is: ________________________

e. A student performs the reaction above and produces 4.6g of calcium chloride. What is his percent yield?

_______________

2. Write the reaction for the combustion of methane (CH4) in pure oxygen to form carbon dioxide and water.

_______________________________________________________

a. What mass of carbon dioxide will be produced by the reaction of 120.0g of methane with 180.0g of of oxygen?

______________

b. The limiting reactant is: ______________________c. The excess reacant is: _______________________

d. A student performs the reaction above, and produces 132g of carbon dioxide. What is his percent yield?

______________

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HW #6: PERCENT YIELD

PERCENT YIELD actual yield x 100PERCENT ERROR actual - theortical x 100theoretical yield theoretical

1. Propane gas burns in oxygen according to the reaction below:

_____C3H8 + _____ O2 _____ CO2 + _____ H2O

A student burns 20.0L of propane gas in excess oxygen at STP. Determine the volume of carbon dioxide that should form in the reaction.

__________________

The reaction only produces 48.0L of carbon dioxide. What is the percent yield?

___________________

What is the percent error?

___________________

2. Sodium chlorate decomposes to produce sodium chloride and oxygen. Write and balance the reaction. The determine the mass of sodium chloride should form if 150g of sodium chlorate decomposes?

Reaction:

____________________

The reaction above is carried out in lab, and 55g of sodium chloride are collected. Determine the percent yield.

____________________

Determine the percent error.

__________________

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