academic chemistry stoichiometry notes - amazon s3 · academic chemistry stoichiometry notes unit...

cincochem.pbworks.com

Name _______________________

Academic Chemistry

Stoichiometry

Notes

Unit #10 Test Date:___________

Resources Unit 10

2 cincochem.pbworks.com Stoichiometry

Common Polyatomic Ions List

Name Ion Name Ion

acetate C2H3O2– or CH3COO– hypochlorite ClO–

ammonium NH4+ nitrate NO3

–

carbonate CO32– nitrite NO2

–

chlorate ClO3– perchlorate ClO4

–

chlorite ClO2– permanganate MnO4

–

chromate CrO42– phosphate PO4

3–

cyanide CN– phosphite PO33–

dichromate Cr2O72– silicate SiO3

2–

hydrogen carbonate HCO3– sulfate SO4

2–

hydroxide OH– sulfite SO32–

1 = I 2 = II 3 = III 4 = IV 5 = V 6 = VI

20 Common Polyatomic Ions

Unit 10 Intro to Stoichiometry

Stoichiometry cincochem.pbworks.com 3

What is stoichiometry?

“Stoich” is the calculation of quantities in chemical reactions.

We understand the LAW of Conservation of Mass, but WHAT does it

mean when we look at chemical reactions?

Before you begin, you need a ________________ chemical reaction.

2H2O 2H2 + 1O2 Conserved?

(equal in reactants and

products)

Atoms = +

Mass = +

Moles = +

Molecules = +

_________________ and________________ are ALWAYS

conserved because of the law of conservation of matter (mass).

__________________ and ______________________ are

NOT ALWAYS CONSERVED because they apply to each compound

(coefficients), not each element.

Converting Moles to Moles Unit 10


How do I solve stoich problems?

1. All stoich questions require you to convert, so you will use

dimensional analysis (railroad tracks).

2. You will need a __________________ chemical equation, so

balance the equation, if necessary.

3. Write your railroad tracks and write the given, just like with moles.

4. You will be converting from one ____________________ in the

reaction to ___________________. So…

5. You will use _____________ ______________* to calculate.

*Mole Ratios use the ___________________ chemical equation to build

ratios to _______________________ between components of a

reaction. They will be conversion factors in your work.

Mole ratios for the decomposition of water:

__2__ H2O __2__ H2 + __1__ O2

mole H2O mole H2O mole O2 mole H2 mole O2 mole H2 mole H2 mole O2 mole H2 mole H2O mole H2O mole O2

Unit 10 Converting Moles to Moles


Mole ratio conversions (basic stoich)

__2__ H2O __2__ H2 + __1__ O2

1) How many moles of hydrogen gas are produced if 5.3 moles of water are decomposed?

2) How many moles of water are needed to form 1.7 moles of oxygen gas?

Practice Using the below reaction, answer the following questions.

__4__ NH3 + __5__ O2 __4__ NO + __6__ H2O

1) When 1.20 moles of ammonia (NH3) are fixed with oxygen, how many moles of nitrogen monoxide (NO) are formed?

2) How many moles of oxygen gas are needed to react with 1.20 moles of ammonia?

Converting Mass to Mass Unit 10


Stoich with mass

1) It’s a lot like solving mass conversions

2) Write the BALANCED equation.

3) Write the given (mass).

4) Convert _______________ to _______________ (using molar mass)

5) Convert _______________ to ________________(using mole ratio)

6) Convert _______________ to _______________ (using molar mass)

Example

__1__ H2O + __1__ Na2O __2__ NaOH

Molar m. = __________ Molar m. = __________ Molar m. = __________

a. Balance the equation

b. Calculate the molar mass of each substance above.

c. How many grams of NaOH are produced whem 12.5 grams of water are combined with sodium oxide (Na2O)?

d. How many grams of Na2O are needed to react with 4.8 grams of water?

Unit 10 Converting Mass to Mass


Practice

_1_ CaC2 + _2_ H2O _1_ C2H2 + _1_Ca(OH)2

How many grams of Ca(OH)2 are produced from 2.5 grams of water

reacting with calcium carbide (CaC2)?

How many grams of CaC2 are needed to react with 9.3 grams of water?

How many grams of C2H2 are produced from 16.6 grams of CaC2?

Molar Volume of a Gas Unit 10


Gases and moles

The volume of a gas changes when _____________________ or

__________________ change. So, gas volume is measured with

those factors removed, at STP, standard temperature and pressure.

To find the ____________________ of ANY gas at STP, we can use

these ratios in our calculations: _____________or _____________

Avogadro’s Hypothesis -Avogadro theorized that equal VOLUMES of

gases at STP contain the same number of _____________________.

SINCE 1 mole = ________ and 1 mol = __________________, we

can say that _____________ = ___________________________

Examples

What is the volume, at STP, of 0.960 mol CH4 gas?

At STP, how many moles are there in 67.2 L of SO2 gas?

Unit 10 Molar Volume of a Gas


Examples, continued

At STP, how many grams are there in 0.880 L helium gas?

Practice How many liters are in 3.70 grams of N2 gas at STP?

How many grams are in 0.44 liters of C2H6 gas at STP?

How many atoms are in 7.6 grams of Ar gas at STP?

Gas Stoichiometry Unit 10


Stoich with gases We can use stoichiometry to calculate gas ________________ in chemical reactions using the relationships between all gases at STP.

Examples

_1_ Sn + _2_ HF _1_ SnF2 + _1_ H2

1. How many liters of HF (a gas) are needed to produce 9.40 liters of hydrogen gas, H2, at STP?

_2_ NH4NO3 _2_ N2 + _4_ H2O + _1_ O2

2. How many liters of N2 are formed when 228 g NH4NO3 is decomposed at STP?

1 Li3N + 3 H2O 1 NH3 + 3 LiOH

3. How many grams of Li3N are needed to produce 15.0 liters of NH3 gas at STP?

Unit 10 Mixed Stoichiometry


Mixed stoichiometry

From mass, particles, or volume, we can use mole ratios convert

between any value of any component of any chemical reaction!

Examples

__4__ Al + __3__ O2 __2__ Al2O3

1. How many moles of aluminum oxide will be produced if 2.5 moles of aluminum are used?

__2__ KClO3 __2__ KCl + __3__ O2

2. How many particles of oxygen gas will be produced if 5.45 grams of potassium chlorate, KClO3, are used?

3. How many liters of oxygen gas will be produced if 7.2 x 1024 formula units of KClO3 are used?

Mixed Stoichiometry Unit 10


Practice

__1__ Fe + __2__ HCl __1__ FeCl2 + __1__ H2

4. How many grams of iron (II) chloride are produced from 6.57 grams of iron?

5. How many liters of hydrogen gas are produced from 14 x 1025 atoms of iron?

Unit 10 Limiting Reactant


Limiting reactant

The limiting reactant is the reactant completely _________________

in the reaction. Other remaining reactants are called ____________.

The reaction ____________ when the limiting reactant is consumed.

The amount of __________________ formed is determined by the

limiting reactant.

How do I determine which reactant is limiting?

1) Using stoich, calculate the ___________ of ______________ (in

grams) that can be formed given the mass of reactant available.

2) Repeat for each _________________. (Usually two reactants!)

3) Whichever reactant yields the smallest mass of product (in

grams) is ___________________.

Examples

__2__ H2 + __1__ O2 __2__ H2O

1. If 100 grams of H2 and 80 grams of O2 are used to produce H2O, which is the limiting reactant?

Limiting Reactant Unit 10


2. If 50 grams of H2 and 100 grams of O2 are used to produce H2O, which is the limiting reactant?

_1_ BaO + _1_ H2SO4 _1_ BaSO4 + _1_ H2O

1. If 28 grams of BaO and 140 grams of H2SO4 are used to produce BaSO4, which is the limiting reactant?

2. If 230 grams of BaO and 98 grams of H2SO4 are used to produce H2O, which is the limiting reactant?

Unit 10 Percent Yield


Percent yield

In a reaction, the ___________________yield is the amount of

product that ____________________ during a real lab investigation.

The _______________________ yield is the ___________________

amount of product that could theoretically be formed (the result of

stoichiometric __________________________).

The percent yield is the _______________ of the actual yield to the

theoretical yield. It measures the ________________________ of

the lab process. It is usually ____________ than 100% (due to

equipment, contamination, lab errors, etc...)

Examples

_2_ Al + _3_ CuSO4 _1_ Al2(SO4)3 + _3_ Cu

If 4.65 grams of Cu are produced when 1.87 grams of Al reacts with excess CuSO4, what is… 1) the actual yield of Cu?

2) the theoretical yield of Cu?

% yield =

Percent Yield Unit 10


3) the percent yield of Cu?

A chemist began with 200 grams of CuSO4. After collecting and drying the product, 61.9 grams of Cu was obtained. What is… 4) the actual yield of Cu?

5) the theoretical yield of Cu?

6) the percent yield of Cu?

Unit 10 Solubility Tables


Extra Credit Unit 10


Unit 10 Extra Credit


Across 2. the reactant that produces the smallest amount

of reactant is called _____ 7. the maximum amount of product that could be

formed, the result of stoich math 8. _____ yield measures the efficiency of a lab

process 10. 6.02 x 1023 particles of a substance

12. any leftover reactants in a reaction are called _____ reactants

14. a _____ compound contains only nonmetals

Down

1. stated that all gases at STP contain equal numbers of particles

3. an _____ compound contains a cation and anion 4. one mole of a gas at stp contains 22.4 _____

5. gas volumes, in stoich, are measured at _____ 6. stoich requires a _____ chemical reaction

9. mole _____ are used to convert from one substance to another in stoich

10. molar _____ is the mass of a mole of a substance

11. the amount of product that forms in a real reaction

13. with mass, always conserved in a reaction

Periodic Table Unit 10


academic chemistry stoichiometry notes - amazon s3 · academic chemistry stoichiometry notes unit...

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