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Chemistry LibreTexts

Homework 1

  • Page ID
    28858
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    Q9.43

    Predict whether a reaction will occur. Balance each equation. If no reaction occurs, state "no reaction"

    \[KBr_{(aq)} + Pb(NO_3)_{2(aq)} \rightarrow\]

    Solution

    Strategy:

    1. Identify each possible ionic compound.
    2. Compare each ionic compounds to the solubility tables. If one of the compounds is insoluble then a reaction has occurred
    3. Write a balanced reaction which includes the insoluble compound on the right hand side. Make sure to include the physical state of each chemical [(aq), (s), etc.]

    A KBr, Pb(NO3)2, KNO3, PbBr2

    B From the solubility tables, most Pb salts are insoluble, including PbBr2

    C KBr(aq) + Pb(NO3)2(aq) -> PbBr2(s) + 2KNO3(aq)

    Q11.55

    Calculate the density of Ne gas at 143 ºC and 4.3 atm.

    Solution

    What we know: Pressure (4.3 atm), temperature (143 ºC ), the identity of the gas (Ne), the molar mass of Ne from the periodic table (20.2 g/mol).

    Asked for: Density of Ne

    Strategy:

    1. The temperature is given in degrees Celsius. This must be converted to Kelvin
    2. Solve for the density

    Solution:

    A Calculate temperature in Kelvin:

    \[T = \rm 143 C + 273 = 416 K\]

    B Calculate the density of Ne:

    \[D = \dfrac{MM\cdot P}{RT}\]

    \[D = \dfrac{\rm 20.2 g/mol \cdot 4.3 \rm atm}{(0.08206 \dfrac{\rm L atm}{\rm mol K}) \rm 416 K}\]

    \[D= \rm 2.54 g/L\]


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