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4.7: Unit 4 Practice Problems

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    260643
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    Problem 1.

    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)
    5. Na(s)+H2O(l)→NaOH(aq)+H2(g)
    6. (NH4)2Cr2O7(s)→Cr2O3(s)+N2(g)+H2O(g)
    Answer 1

    PCl5(s)+H2O(l)→POCl3(l)+2HCl

    Answer 2

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

    Answer 3

    H2(g)+I2(s)→2HI(s)

    Answer 4

    4Fe(s)+3O2(g)→2Fe2O3(s)

    Answer 5

    2Na(s)+2H2O(l)→2NaOH(aq)+H2(g)

    Answer 6

    (NH4)2Cr2O7(s)→Cr2O3(s)+N2(g)+4H2O(g)

    Question 2.

    Write the balanced chemical equation for the combustion of gaseous butane, C4H10.  

    Answer 

    2C4H10(g)+13O2(g)→8CO2(g)+10H2O(g)

    Question 3.

    What is the mass of 0.54mole of CO2?

    Answer
    \[\mathrm{0.54\: \cancel{mole} \times \dfrac{44\: g}{1\:\cancel{mole}}=24\: g}\]

    Question 4.

    230 grams of O is how many moles of O?

    Answer
    \[\mathrm{230\: \cancel{g} \times \dfrac{1\: mole}{16\:\cancel{g}}=14\: mole O}\]

     

    Question 5. 

    What is the mass of 1.00 mole of magnesium nitrate?         

    Answer
    The formula for magnesium nitrate is Mg(NO3)2     mass = (1 x 24.31) + (2 x 14.01) + (6 x 16.00) = 148 g Mg(NO3)2

        

    Question 6.

    How many atoms are on 1.76 moles of phosphorus?

    Answer
    \[\mathrm{1.76\: \cancel{mole} \times \dfrac{6.02e23\: atoms}{1\:\cancel{mole}}=1.06e24\: atoms}\]              1.06x1024atoms

     

    Question 7.

    What is the mass of 3.57x1024molecules of CaS?

    Answer
    clipboard_e4bf190643533f3609321e40057fd8dda.png

    Question 8.

    Automotive air bags inflate when a sample of sodium azide, NaN3, is very rapidly decomposed.

    2NaN3(s)→2Na(s)+3N2(g)

    If this reaction begins with only 1.46 moles of NaN3, how many moles of nitrogen gas, N2, will be produced?

    Answer
    clipboard_ec0c067752d17e7d8475307e5330f0adc.png

    Question 9.

    What mass of silver oxide, Ag2O, is required to produce 25.0 g of silver sulfadiazine, AgC10H9N4SO2, from the reaction of silver oxide and sulfadiazine?

    2C10H10N4SO2+Ag2O→2AgC10H9N4SO2+H2O

    Answer

    clipboard_e7c8c7d035423549bd6df69395e895bc0.png

    = 8.11 g Ag2O

    Question 10.

    Identify the energy graphs A and B as being for an endothermic or exothermic reaction.

    A. 

    clipboard_ef90d9b13892942c8b50bdbbfa3239c5d.png

    B. 

    clipboard_e36458a3aea1a579b746190193ee1dc03.png

    Answer
    A. exothermic      B. endothermic

     

     


    4.7: Unit 4 Practice Problems is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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