chemical-reactions-and-stoichiometry-unit by huanghengdong

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									                  TYPES OF CHEMICAL REACTIONS ( A GENERAL SURVEY)
1) Combustion: A combustion reaction is when oxygen combines with another compound to form water and carbon
dioxide. These reactions are exothermic, meaning they produce heat. An example of this kind of reaction is the burning of
napthalene:

                                             C10H8 + 12 O2 ---> 10 CO2 + 4 H2O




2) Synthesis: A synthesis reaction is when two or more simple compounds combine to form a more complicated one.
These reactions come in the general form of:

                                                     A + B ---> AB
One example of a synthesis reaction is the combination of iron and sulfur to form iron (II) sulfide:
                                                 8 Fe + S8 ---> 8 FeS


3) Decomposition: A decomposition reaction is the opposite of a synthesis reaction - a complex molecule breaks down to
make simpler ones. These reactions come in the general form:

                                                     AB ---> A + B
One example of a decomposition reaction is the electrolysis of water to make oxygen and hydrogen gas:
                                                  2 H2O ---> 2 H2 + O2


4) Single displacement: This is when one element trades places with another element in a compound. These reactions
come in the general form of:

                                                  A + BC ---> AC + B
One example of a single displacement reaction is when magnesium replaces hydrogen in water to make magnesium
hydroxide and hydrogen gas:
                                            Mg + 2 H2O ---> Mg(OH)2 + H2


5) Double displacement: This is when the anions and cations of two different molecules switch places, forming two
entirely different compounds. These reactions are in the general form:

                                                AB + CD ---> AD + CB
One example of a double displacement reaction is the reaction of lead (II) nitrate with potassium iodide to form lead (II)
iodide and potassium nitrate:
                                        Pb(NO3)2 + 2 KI ---> PbI2 + 2 KNO3


6) Acid-base: This is a special kind of double displacement reaction that takes place when an acid and base react with
                   +                                   -
each other. The H ion in the acid reacts with the OH ion in the base, causing the formation of water. Generally, the
product of this reaction is some ionic salt and water:

                                               HA + BOH ---> H2O + BA
One example of an acid-base reaction is the reaction of hydrobromic acid (HBr) with sodium hydroxide:
                                             HBr + NaOH ---> NaBr + H2O
                               Types of Reactions Worksheet
Balance the following equations and indicate the type of reaction taking place:

1)     ____ NaBr + ____ H3PO4  ____ Na3PO4 + ____ HBr

                                                                     Type of reaction: ____________________


2)     ____ Ca(OH)2 + ____ Al2(SO4)3  ____ CaSO4 + ____ Al(OH)3

                                                                     Type of reaction: ____________________


3)     ____ Mg + ____ Fe2O3  ____ Fe + ____ MgO

                                                                     Type of reaction: ____________________


4)     ____ C2H4 + ____ O2  ____ CO2 + ____ H2O

                                                                     Type of reaction: ____________________


5)     ____ PbSO4  ____ PbSO3 + ____ O2

                                                                     Type of reaction: ____________________


6)     ____ NH3 + ____ I2  ____ N2I6 + ____ H2

                                                                     Type of reaction: ____________________


7)     ____ H2O + ____ SO3  ____ H2SO4

                                                                     Type of reaction: ____________________


8)     ____ H2SO4 + ____ NH4OH  ____ H2O + ____ (NH4)2SO4


                                                                   Type of reaction: ____________________
                                        Balancing Reactions

#1-3 a. Identify Type AND write the formulas b. Balance the Reaction

1. Silver nitrate + Calcium chloride Silver Chloride + Calcium Nitrate

a._________________    ______________________________________________________________


b._________________________________________________________________________________

2. The reaction of nitrogen monoxide with hydrogen to produce nitrogen and water:

a.___________________     ____________________________________________________________


b._________________________________________________________________________________

3. Synthesis of sulfur dioxide from sulfur and oxygen

a.____________________     ___________________________________________________________


b._________________________________________________________________________________


# 4-10 a. Identify the type AND Write the name of the predicted products, b. write the entire reaction
with formulas, c. write the reaction as a balanced chemical reaction

4. Decomposition of ammonia (NH3):

a.____________________     ___________________________________________________________


b._________________________________________________________________________________


c._________________________________________________________________________________

5. Sodium + Hydrogen hydroxide

a._____________________     __________________________________________________________


b._________________________________________________________________________________


c._________________________________________________________________________________
6. The combustion of ethanol (C2H5OH):

a.______________________       ________________________________________________________


b._________________________________________________________________________________


c._________________________________________________________________________________


7. The combustion of C10H22:

a._______________________       ________________________________________________________


b._________________________________________________________________________________


c._________________________________________________________________________________


8. Synthesis of diphosphorous pentoxide (Write the name of the reactants for this one)

a.__________________________       _____________________________________________________


b._________________________________________________________________________________


c._________________________________________________________________________________


9. Barium hydroxide + Hydrogen Phosphate

a.__________________    _____________________________________________________________


b._________________________________________________________________________________


c._________________________________________________________________________________

10. Potassium bromide + chlorine

a._____________________     ___________________________________________________________


b._________________________________________________________________________________


c._________________________________________________________________________________
PRACTICE: FOR EACH OF THE FOLLING: WRITE THE BALANCED CHEMICAL REACTION
Silver nitrate + Calcium chloride
Silver Chloride + Calcium Nitrate
The reaction of nitrogen monoxide with hydrogen to produce nitrogen and water:
Synthesis of sulfur dioxide
Decomposition of ammonia (NH3):
Sodium + Hydrogen hydroxide
The combustion of ethanol (C2H5OH):
The combustion of C10H22: .
Synthesis of diphosphorous pentoxide
Barium hydroxide + Hydrogen Phosphate
Potassium bromide + chlorine
Silver nitrate + Copper (II) chloride
Decomposition of potassium chlorate into potassium chloride and oxygen gas:
Synthesis of carbon monoxide
Calcium + Hydrogen hydroxide
The combustion of benzene (C6H6)
The combustion of C3H7OH:
Sodium hydroxide + Hydrogen Carbonate
Potassium sulfide + fluorine
                                            STOICHIOMETRY

Stoichiometry is the calculation of chemical quantities from balanced equations.
The four quantities involved in stoichiometric calculations are:
       particles - the relative amounts of atoms, ions, formula units, or molecules in various reactants or
       products
       moles - the relative number of moles of reactants or products
       mass - the relative masses of reactants or products
       volume - the relative amounts of gaseous reactants or products

Atoms and mass are always conserved in chemical reactions.

Here is an example of a balanced chemical equation with some chemical quantities listed below them.
        4 Na(s) + O2(g)  2 Na2O(s)
        4 atoms + 1 molecule 2 formula units
        4 moles + 1 mole _ 2 moles
        91.96 g + 32.00 g _ 123.96 g

Here are some calculations that can then be performed :
a. If 3.50 moles of Na2O are needed, how many moles of sodium will be required (assuming sufficient oxygen




b. If you have 45.00 g Na and an abundant supply of oxygen, how much Na2O should be produced?




c. If you had an abundant supply of oxygen and needed to produce 12.2 moles of Na2O, how many grams of
sodium would you need?




d. How many formula units of Na2O could be produced from 500.0 g of sodium metal? This one is a little
trickier so you need to plan ahead. From grams of Na you can determine moles of Na. From moles Na you can
calculate moles Na2O from the mole ratio, and then from moles of Na2O you can calculate unit formulas of
Na2O.




e. How many liters of oxygen will be needed to react with 15.0 g of sodium if at STP? If air is 22.5 % oxygen
by volume, how many liters of air will be needed.
Sample Stoichiometry Problems;

1. Write the balanced reaction for the combustion of ethanol (C2H5OH);


a. How many grams of ethanol are required to react with 500.00 grams of oxygen?




b. If 1.50 grams of ethanol is burned:
        i. how many liters of oxygen will be required? If air is 27.50 % oxygen by volume, how many liters of
        air would be required?



       ii. how many liters of carbon dioxide will be produced?



       iii. how many grams of water are produced?




2. The fertilizer ammonium sulfate is prepared by the reaction of ammonia and sulfuric acid.
Write the balanced chemical reaction:



a. How many L of NH3 are needed to make 1.00 x 105 kg of fertilizer?



b. how many moles of sulfuric acid are required to react with 15.60 moles of ammonia?



3. Silicone tetrachloride is prepared by heating silicon in chlorine gas. Write the balanced chemical reaction:



a. If .507 mol of SiCl4 are produced, how many moles of molecular chlorine were used?



b. How many grams of silicone were needed.
                     LIMITING AND EXCESS REACTANTS IN STOICHIOMETRY
                             YOU MUST COMPARE MOLES OF EACH

1. For the reaction: 2 CO + O2  2 CO2,
a.determine the moles of CO2 produced for each of the following Mixtures of CO and O2:
b. id the LR and X-S reactant
c. for the X-S reactant, calculate how many moles are in excess

Moles of CO                           Moles of O2                         Moles of CO2
1.00                                  1.00
1.00                                  2.00
2.00                                  1.00
2.00                                  3.00
3.00                                  2.00
10.00                                 7.00


2. Ozone (O3) in the atmosphere can react with nitrogen monoxide to produce oxygen and nitrogen dioxide.
Write the balanced chemical reaction:



a. If .740 g of O3 are allowed to react .670 g of NO:
        i. How many moles of each are reacting?


       ii. How many moles of NO2 are produced? How many grams of NO2 are produced?


       iii. How many L of O2 are produced?


       iv. What is the X-S reactant, how many moles are in excess? How many grams are in X-S?



3. You are given 10.0 g of sodium and 10.0 grams of oxygen to use in the synthesis of sodium oxide.
You know what to do first!!!



a. How much sodium oxide will be produced?


b. What is the x-s reactant? What mass is in x-s?


c. If the oxygen comes from air, and the air used is 25.0 % oxygen by volume, how many liters of air would be
required?
4. Balance the following:     ___ C6H10 + ___ O2  ___ CO2 + ___ H2O

a. If I do this reaction with 35 grams of C6H10 and 45 grams of oxygen, how many grams of carbon dioxide will
be formed?




b. What is the limiting reagent for problem 6? ___________

c. How much of the excess reagent is left over after the reaction from problem 6 is finished?
                           PERCENT YIELD STOICHIOMETRY PROBLEMS

PERCENT YIELD IS A RATIO MEASUREMENT OF WHAT YOU ACTUALLY MAKE TO WHAT YOU
CALCULATE YOU SHOULD MAKE.

% YEILD = QUANTITY OF PRODUCT YOU ACTUALLY MAKE                                x 100
           QUANTITY OF PRODUCT YOU SHOULD MAKE
          (use stoichiometry to calculate this quantity)

or

% YIELD = EXPERIMENTAL QUANTITY PRODUCED                            X 100
           THEORETICAL QUANTITY PRODUCED

Examples:
#1 Find % yield

A student reacts 5.00 grams of magnesium with excess oxygen in a typical lab experiment.
The product (MgO) weighs 7.95 grams. What is the percent yield?




#2 Calculation of the Actual quantity

 The production of Ammonia from hydrogen gas and nitrogen gas has a 95.9 % yield.
How much ammonia can actually be obtained with reacting 1500 kL of hydrogen with
1000 kL of nitrogen. (note-this is a limiting reactant problem also.




#3 Calculate the quantity of reactant necessary to obtain a certain amount of a product.

Ethylene (C2H4), an important industrial organic chemical, can be prepared by heating hexane
(C6H14) at 800 Co:
                        C6H14  C2H4 + other products (the 1:1 ratio is accurate)
If the percent yield of ethylene in this reaction is 42.5%, what mass of hexane must be reacted to
produce 481 grams of ethylene?
             USING SOLUTION CONCENTRATIONS IN REACTION STOICHIOMETRY

MOLARITY (M)= MOLES OF SOLUTE/LITER OF SOLUTION
Solute is what you are dissolving.
Solvent is what you are dissolving the solute in.

1. A STUDENT REACTS 25.0 mL OF .850 M HYDROCHLORIC ACID WITH
A STRIP OF MAGNESIUM RIBBON:

A. WRITE THE BALANCED CHEMICAL REACTION



B. HOW MANY MOLES OF HYDROCHLORIC ACID ARE REACTING?




C. WHAT VOLUME OF HYDROGEN WILL BE PRODUCED AT STP?




D. WHAT MASS OF MAGNESIUM RIBBON WILL REACT?




II. A STUDENT REACTS A SAMPLE OF SODIUM BICARBONATE WITH
20.0 mL HYDROCHLORIC ACID ACCORDING TO THE FOLLOWING REACTION:
NaHCO3 + HCl  NaCl + H2O + CO2, THE REACTION PRODUCES 125 mL OF
CARBON DIOXIDE AT STP.

A. BALANCE THE REACTION:


B. HOW MANY MOLES OF HCl WERE REACTED?




C. WHAT WAS THE CONCENTRATION OF THE HCl SOLUTION?




D. HOW MANY GRAMS OF NaHCO3 WERE USED AND WHAT VOLUME OF CO2 AT STP WILL BE
PRODUCED?
                                           EXTRAS JUST FOR YOU!


1. What mass of silver can be obtained by the reaction of a large excess of copper metal with 5.10 g of
AgNO3 in aqueous solution? Cu + 2 AgNO3  Cu(NO3)2 + 2 Ag

2. How many liters of oxygen are required to react with 2.50 g of Magnesium at STP?
Mg + O2  2 MgO

3. What is the molarity of a solution prepared by dissolving 17.1 g of ordinary sugar (sucrose: C12H22O11)
in enough water to make .500 L of solution. This is not a stoichiometry problem!

4. How many grams of sodium chloride are required to produce 1.00 L of .250 M soloution?

5. When MoO3 and zinc are heated together they react: 3 Zn + 2MoO3 Mo2O3 + 3ZnO.
What mass of zinc oxide is formed when 10.0 g of zinc react with 20.0 g of MoO3?

6. When 11.6 g of unknown compound XCl2 is reacted with excess silver nitrate, 28.66 g of AgCl is formed.
XCl2 + 2 AgNO3  2 AgCl + X(NO3)2.

a.   how many moles of AgCl were formed
b.   how many moles of XCl2 were used in the reaction
c.   what is the molar mass of XCl2
d.   what is the atomc mass of X and identify the element

7. What is its molarity of the following pure solutions with the given density
a. ethanol has a density of .789 g/ml.       b. sulfuric acid has a density of 1.841 g/ml

8. 75.0 mL of .250 M hydrochloric acid reacts with Magnesium to produce hydrogen gas.
Mg +2 HCl  MgCl2 + H2
a. How many liters of Hydrogen will be produced at STP
b. How many grams of magnesium were reacted.

9. 15.0 mL of 3.0 M hydrochloric acid are reacted with 25.0 mL of 2.5 M NaOH
a.Which reactant is in excess, how many mL.
b. how many grams of water are expected to be produced?

								
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