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Chemistry LibreTexts

Homework 57

  • Page ID
    28971
  • Q 9.40

    Of the given compounds, tell which are strong electrolytes and which are non electrolytes:

    A. HCl B. H2SO4 C. CH3OH D. CO2

    solution

    Strategy and hints:

    • Strong electrolytes are compounds that completely break up into ions when they dissolve in water.
    • nonelectrolytes are compounds that only break up into molecules when in water and do not form ions
    • start by separating the compounds and identify the ionic ones
    • next, use the characteristics of strong electrolytes and nonelectrolytes to determine what each compound should be classified as

    A. H+ & Cl- --> strong electrolyte

    B. molecular compound --> nonelectrolyte

    C. H+ & SO42- --> strong electrolyte

    D. molecular compound --> nonelectrolyte

    Helpful resources:

    Q10.50

    Ethane has a change in enthalpy of 5500.2 kJ when 1.0 mol is combusted at 1.0 atm with a change of internal energy of 5512.4 kJ. Calculate the amount of work done during combustion.

    solution

    Strategy and hints:

    • write out down the "givens" in the problem
    • choose the correct equation to determine the answer with the information you are given
    • make sure your signs are correct

    ΔEsystem=q+w ΔH = ΔE +ΔPV w= -PΔV

    so, ΔE=ΔH+w

    w=ΔH-ΔE

    ΔE= 5512.4 kJ

    ΔH= 5500.2 kJ

    w= 5500.2 kJ - 5512.4kJ = -12.2 kJ

    Helpful resources:

    http://chemwiki.ucdavis.edu/Physical...s_in_Reactions

    http://chemwiki.ucdavis.edu/Physical...y_Calculations

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