Homework 1

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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:

Identify each possible ionic compound.
Compare each ionic compounds to the solubility tables. If one of the compounds is insoluble then a reaction has occurred
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:

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

Solution:

A Calculate temperature in Kelvin:

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

B Calculate the density of Ne:

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

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

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