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5: Chemical Reactions

  • Page ID
    281552
  • Introduction to Chemical Reactions

    Exercise \(\PageIndex{1a}\)

    From the statement “nitrogen and hydrogen react to produce ammonia,” identify the reactants and the products.

    Answer

    reactants: nitrogen (N2) and hydrogen (H2)

    product: ammonia (NH3)

    Exercise \(\PageIndex{1b}\)

    From the statement “sodium hydroxide and water are produced when sodium metal reacts with water” identify the reactants and the products.

    Answer

    reactants: sodium (Na) and water (H2O)

    products: sodium hydroxide (NaOH) and hydrogen (H2)

     

    Exercise \(\PageIndex{1c}\)

    What does it mean to say an equation is balanced? Why is it important for an equation to be balanced?

    Answer

    An equation is balanced when the same number of each element is represented on the reactant and product sides. Equations must be balanced to accurately reflect the law of conservation of matter.

     

     

     

    Types of Chemical Reactions

     

    Exercise \(\PageIndex{2a}\)

    Identify the type of reaction

    1. 2C2H6 + 7O2 → 4CO+ 6H3O
    2. 2HCl + Na2S → 2NaCl + H2S
    3. 2SO2 + O2 → 2SO3
    4. Zn + Fe(NO3)2 → Zn(NO3)2 + Fe
    Answer a

    combustion

    Answer b

    double displacement

    Answer c

    formation (synthesis)

    Answer d

    Single displacement 

     

     

    Balancing Chemical Equations

    Exercise \(\PageIndex{3a}\)

    Balance the following equations

    1. PCl5(s)+H2O(l) → POCl3(l)+HCl(aq)
    2. Cu(s)+HNO3(aq) → Cu(NO3)2(aq)+H2O(l)+NO(g)
    3. H2(g)+I2(s) → HI(s)  
    4. Fe(s)+O2(g) → Fe2O3(s)
    Answer a

    PCl5(s)+H2O(l)→POCl3(l)+2HCl(aq)

    Answer b

    3Cu(s)+8HNO3(aq)→3Cu(NO3)2(aq)+4H2O(l)+2NO(g)

    Answer c

    H2(g)+I2(s)→2HI(s)

    Answer d

    4Fe(s)+3O2(g)→2Fe2O3(s)

     

    Exercise \(\PageIndex{3b}\)

    Balance the following equations

    1. Na(s)+H2O(l) → NaOH(aq)+H2(g)
    2. (NH4)2Cr2O7(s) → Cr2O3(s)+N2(g)+H2O(g)
    3. P4(s)+Cl2(g) → PCl3(l)  
    4. PtCl4(s) → Pt(s)+Cl2(g)
    Answer a

    2Na(s)+2H2O(l) → 2NaOH(aq)+H2(g)

    Answer b

    (NH4)2Cr52O7(s) → Cr2O3(s)+N2(g)+4H2O(g)

    Answer c

    P4(s)+6Cl2(g) → 4PCl3(l)

    Answer d

    PtCl4(s) → Pt(s)+2Cl2(g)

     

    Exercise \(\PageIndex{3c}\)

    Balance the following equations

    1. Ag(s)+H2S(g)+O2(g) → Ag2S(s)+H2O(l)  
    2. P4(s)+O2(g)→P4O10(s)
    3. Pb(s)+H2O(l)+O2(g)→Pb(OH)2(s)
    4. Fe(s)+H2O(l)→Fe3O4(s)+H2(g)
    Answer a

    4Ag(s)+2H2S(g)+O2(g) → 2Ag2S(s)+2H2O(l)  

    Answer b

    P4(s)+5O2(g)→P4O10(s)

    Answer c

    2Pb(s)+2H2O(l)+O2(g)→2Pb(OH)2(s)

    Answer d

    3Fe(s)+4H2O(l)→Fe3O4(s)+4H2(g)

    Exercise \(\PageIndex{3c}\)

    Balance the following equations

    1. Sc2O3(s)+SO3(l)→Sc2(SO4)3(s)
    2. Ca3(PO4)2(aq)+H3PO4(aq)→Ca(H2PO4)2(aq)
    3. Al(s)+H2SO4(aq)→Al2(SO4)3(s)+H2(g)
    4. TiCl4(s)+H2O(g)→TiO2(s)+HCl(g)
    Answer a

    Sc2O3(s)+3SO3(l)→Sc2(SO4)3(s)

    Answer b

    Ca3(PO4)2(aq)+4H3PO4(aq)→3Ca(H2PO4)2(aq)

    Answer c

    2Al(s)+3H2SO4(aq)→Al2(SO4)3(s)+3H2(g)

    Answer d

    TiCl4(s)+2H2O(g)→TiO2(s)+4HCl(g)

     

    Aqueous Reactions

    Solubility Rules

    Exercise \(\PageIndex{4a}\)

    Use the solubility rules to determine if the following compounds are soluble or insoluble. Indicate answer by writing formula followed by (aq) for soluble and (s) for insoluble.

    1. NaCl(?)
    2. Pb(OH)2(?)
    3. MgF2(?)  
    4. K2SO4(?) 
    Answer a

    NaCl(aq)

    Answer b

    Pb(OH)2(s)

    Answer c

    MgF2(s)

    Answer d

    K2SO4(aq) 

     

    Exercise \(\PageIndex{4b}\)

    Use the solubility rules to determine if the following compounds are soluble or insoluble. Indicate answer by writing formula followed by (aq) for soluble and (s) for insoluble.

    1. AgCl(?)
    2. PbCl2(?)
    3. Ba(OH)2(?)  
    4. Pb3(PO4)2(?) 
    Answer a

    AgCl(s)

    Answer b

    PbCl2(s)

    Answer c

    Ba(OH)2(aq)  

    Answer d

    Pb3(PO4)2(s) 

     

    Exercise \(\PageIndex{4c}\)

    Identify the following as a strong electrolyte, a weak electrolyte, or a non-electrolyte, and why

    1. NaCl(aq)
    2. Na2SO4(aq)
    3. C6H12O6(aq)  (sugar)
    4. AgCl(s) 
    Answer a

    strong electrolyte, soluble salt

    Answer b

    strong electrolyte, soluble salt

    Answer c

    nonelectrolyte, soluble molecule

    Answer d

    nonelectrolyte, insoluble salt

    Predicting Products and Balancing Eqs

     

    Exercise \(\PageIndex{4d}\)

    Predict products and balance the equation

    1. Al(NO3)3(aq) +  Na2(CO3)(aq) 
    2. Pb(ClO4)2(aq) +  Na2SO4(aq)
    3. (NH4)3PO4(aq)  + NaOH(aq) 
    4. (NH4)3PO3(aq)  +  CaSO4(aq)
    Answer a

    2 Al(NO3)3(aq) +  3 Na2(CO3)(aq)  -> Al2(CO3)3(s) + 6 NaNO3(aq)

    Answer b

    Pb(ClO4)2(aq) +  Na2SO4(aq)  -> PbSO4(s) +  2 NaClO4(aq)

    Answer c

    (NH4)3PO4(aq)  + 3 NaOH(aq) -> 3NH4OH(aq)  +  Na3PO4(aq)

    Answer d

     2(NH4)3PO4(aq)  + 3 CaSO4(aq) -> 3(NH4)2SO4(aq)  +  Ca3(PO4)2(S)

    f

    Exercise \(\PageIndex{4e}\)

    Predict products and balance the equation

    1. (NH4)2SO4(aq)  +   CaCl2(aq)  
    2. AgCH3CO2 (aq)  +  KCl(aq)
    3. Pb(NO3)2(aq)  +  Na2SO4(aq)   
    4. NaOH  +  CaCl2(aq)
    Answer a

    (NH4)2SO4(aq)  +   CaCl2(aq) -> CaSO4(s) +  2 NH4Cl(aq)

    Answer b

    AgCH3CO2 (aq)  +  KCl(aq)  -> AgCl(s)  + KCH3CO2(aq)

    Answer c

    Pb(NO3)2(aq)  +  Na2SO4(aq) ->  PbSO4(s)+  2 NaNO3(aq)

    Answer d

    2 NaOH  +  CaCl2(aq) -> 2 NaCl(aq) + Ca(OH)2

    Exercise \(\PageIndex{4f}\)

    Predict products and balance the equation

    1. BaI2(aq) + H2SO4 (aq)
    2. Mg(s)  +   FeCl3(aq)
    3. AgNO3(aq)  +  Ca(s) 
    4. Na(s)  +  HCl(aq)
    5. Na(s)  +  H2O(l) 
    Answer a

    BaI2  + H2SO4(aq) ->  2 HI(aq) + BaSO4(s)

    Answer b

     3 Mg(s)  +  2 FeCl3(aq)  -> 2 Fe(s) + 3 MgCl2(aq)

    Answer c

    2 AgNO3(aq)  +  Ca(s)-> 2 Ag(s) + Ca(NO3)2(aq)

    Answer d

    2 Na(s)  +  2 HCl(aq) ->  H2(g)  +  2 NaCl(aq)

    Answer e

    2 Na(s)  +  2 H2O(l)  ->   H2(g)  +  2 NaOH(aq)

    Net, Total and General Ionic Eqs 

    Exercise \(\PageIndex{4g}\)

    Predict products, write general, total ionic and net ionic equations (this is problem 5.4d above)

    1. Al(NO3)3(aq) +  Na2(CO3)(aq) 
    2. Pb(ClO4)2(aq) +  Na2SO4(aq)
    3. (NH4)3PO4(aq)  + NaOH(aq) 
    4. (NH4)3PO3(aq)  +  CaSO4(aq)
    Answer a

    2 Al(NO3)3(aq) +  3 Na2(CO3)(aq)  -> Al2(CO3)3(s) + 6 NaNO3(aq)   (general)

    2Al+3(aq) +6NO3-(aq) + 6Na+(aq)+3CO3-2(aq)  -> Al2(CO3)3(s) + 6Na+(aq)+ 6NO3-(aq)   (total ionic)

    2Al+3(aq) +3CO3-2(aq)  -> Al2(CO3)3(s)  (net ionic)

     

    Answer b

    Pb(ClO4)2(aq) +  Na2SO4(aq)  -> PbSO4(s) +  2 NaClO4(aq)  (general)

    Pb+2(aq) +2ClO4-(aq) +  2Na+(aq) + SO4-2(aq)  -> PbSO4(s) +   2Na+(aq) + 2ClO4-(aq)  (total ionic)

    Pb+2(aq) + SO4-2(aq)  -> PbSO4(s)    (net ionic)

    Answer c

    (NH4)3PO4(aq)  + 3 NaOH(aq) -> 3NH4OH(aq)  +  Na3PO4(aq)  (general)

    3NH4+(aq)+ PO4-3(aq) + 3Na+(aq) + 3OH-(aq) -> 3NH4+(aq)+ PO4-3(aq) + 3Na+(aq) + 3OH-(aq) (total ionic)

    no reaction   (net ionic)

    Answer d

     2(NH4)3PO4(aq)  + 3 CaSO4(aq) -> 3(NH4)2SO4(aq)  +  Ca3(PO4)2(S)     (general)

    6NH4+(aq)+ PO4-3(aq) + 3Ca+2(aq) + SO4-2(aq) -> 6NH4+(aq)+ 3SO4-2(aq) +  Ca3(PO4)2(S)     (total ionic)

     PO4-3(aq) + 3Ca+2(aq) -> Ca3(PO4)2(S)     (total ionic)

     

    Neutralization Reactions

    Exercise \(\PageIndex{5a}\)

    Answer the following

    1. What is the Arrhenius definition of an acid?  
    2. What is the Arrhenius definition of an base?
    3. What is the Bronsted definition of an acid?  
    4. What is the Bronsted definition of an base?  
    Answer a

    Substance which increases hydronium ion concentration in water

    Answer b

    substance that increases hydroxide concentration in water

    Answer c

    Proton donor

    Answer d

    proton acceptor

     

    Exercise \(\PageIndex{4g}\)

    Predict products, write general, total ionic and net ionic equations 

    1. HNO3(aq) +  NaOH(aq) 
    2. Ba(OH)2(aq) +  H2SO4(aq)
    3. HC2H3O2(aq)  + NaOH(aq) 
    4. H3PO3(aq)  +  Ca(OH)2(aq)
    Answer a

    HNO3(aq) +  NaOH(aq)  -> NaNO3(aq) + H2O(l)   (general)

    H+(aq) +NO3-(aq) + Na+(aq)+OH-(aq)  -> H2O(l) +NO3-(aq) + Na+(aq)     (total ionic)

    H+(aq) +OH-(aq)  -> H2O(l)        (net ionic)

     

    Answer b

    Ba(OH)2(aq) +  H2SO4(aq)  -> BaSO4(s) +  2H2O(l)  (general)

    Ba+2(aq) +2OH-(aq) +  2H+(aq) + SO4-2(aq)  -> BaSO4(s) +  2H2O(l)  (total ionic)

    Ba+2(aq) +2OH-(aq) +  2H+(aq) + SO4-2(aq)  -> BaSO4(s) +  2H2O(l)    (net ionic)

    Answer c

    HC2H3O2(aq)  +  NaOH(aq) -> NaC2H3O2(aq)  +  H2O(l)  (general)

    HC2H3O2(aq)  +  Na+(aq)+ OH-(aq) -> Na+(aq) + C2H3O2-(aq)  +  H2O(l) (total ionic)

    HC2H3O2(aq)  +  OH-(aq)  ->  C2H3O2-(aq)  +  H2O(l)   (net ionic)

    Answer d

    H3PO4(aq)  +  3NH4OH(aq) -> (NH4)3PO4(aq)  + 3H2O(l)       (general)

    H3PO4(aq)  +  3NH4+(aq) + 3OH-(aq) -> 3NH4+(aq) +PO4-3(aq)  + 3H2O(l)      (total ionic)

    H3PO4(aq)  +  3OH-(aq) -> PO4-3(aq)  + 3H2O(l)     (total ionic)

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