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Chemical Reaction and Stoichiometry Questions

1.        Balance the following chemical reactions:

BaCl2 (aq)            +          Na2SO4 (aq)                  -›     BaSO4 (s)                       +          NaCl (aq)

Cu (s)                                  +          AgNO3 (aq)                    -›     Ag (s)                                  +          Cu(NO3)2 (aq)

Fe (s)                                  +          O2 (g)                                   -›     Fe2O3 (s)

P4 (s)                                    +          S­8 (s)                                    -›     P2S5 (s)

NaHSO4 (s)                  -›     Na2S2O7 (s)                   +          H2O (l)

HNO3 (aq)                        -›     NO2 (g)                              +          H2O (l)                                +          O2 (g)

HNO3 (aq)                        -›     Al(OH)3 (s)                     +          Al(NO3)3 (aq)                +          H2O (l)

K2Cr2O7 (s)                    -›     K2CrO4 (s)                      +          Cr2O3 (s)                           +          O2 (g)

2.        Which of the following are true statements about any chemical reaction?

(I) The number of each atom is conserved

(II) The number of each molecule is conserved

(III) Mass is conserved

(IV) The number of moles of product equals the number of moles of reactant

(V) In order for a reaction to occur, atoms must recombine in new formations

(a) (II), (III), (V) are correct

(b) (I), (IV) are correct

(c) (I), (V) are correct

(d) Only (III) is correct

(e) (I), (III), (V) are correct

(f) (II), (III) are correct

3.        Given the reaction, answer the questions below.

(a) Balance the reaction : C3H8 + O2 -› CO2 + H2O

(b) If 7 moles of oxygen reacts with excess C3H8, how much carbon dioxide will form?

(c) If 3 moles of oxygen reacts, how many moles of CO2 will form?

(d) If 3 moles of oxygen reacts, how many grams of H2O will form?

 

4.        Given the reaction, answer the questions below.  Assume 6.20 grams of

NH3 (g)       +          O­2 (g)           -›     N2 (g)           +          H2O (g)

(a) How many moles of NH3 react?

(b) How many moles of oxygen are needed to fully react?

(c) Given the values in (a) and (b), how many grams of water will be produced?

(d) What volume of oxygen at STP is needed?

(e) What volume of nitrogen gas at STP is produced?

(f) How many molecules of water will be produced?

 

Answers

1.

            BaCl2 (aq)            +          Na2SO4 (aq)                  -›     BaSO4 (s)                       +          2 NaCl (aq)

            Cu (s)                                  +          2 AgNO3 (aq)               -›     2 Ag (s)                             +          Cu(NO3)2 (aq)

            4 Fe (s)                            +          3 O2 (g)                             -›     2 Fe2O3 (s)

            4 P4 (s)                              +          5 S­8 (s)                              -›     8 P2S5 (s)

            2 NaHSO4 (s)             -›     Na2S2O7 (s)                   +          H2O (l)

            4 HNO3 (aq)                  -›     4 NO2 (g)                         +          2H2O (l)                        +          O2 (g)

            3 HNO3 (aq)                  -›     Al(OH)3 (s)                     +          Al(NO3)3 (aq)                +          3 H2O (l)

            4 K2Cr2O7 (s)               -›     4 K2CrO4 (s)                 +          2 Cr2O3 (s)                     +          3 O2 (g)

 

2.         (e)

 

3.        

(a) C3H8 + 5O2 -› 3CO2 + 4H2O

(b) 4.2 moles CO2

(c) 1.8 moles CO2

(d) 43.2 g H2O

 

4.         Formula must be balanced first

4NH3 (g)                           +          3O­2 (g)       -›     2N2 (g)        +          6H2O (g)

(a) 0.365 moles NH3

(b) 0.274 moles O2

(c) 9.847 g water (H2O)

(d) 6.139 L

(e) 4.09 L

(f) 3.29 x 1023 molecules of water

 

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