If 43 g of ammonium chloride undergoes a double replacement reaction with 76 g o
ID: 799559 • Letter: I
Question
If 43 g of ammonium chloride undergoes a double replacement reaction with 76 g of sodium nitrite, and all the ammonium nitrite that was formed decomposes to nitrogen gas and liquid water in a sealed 0.3 liter flask (originally a vacuum- with no gas) inside a small bomb calorimeter with 400 g water starting at 25.00 degrees C, what becomes the pressure in the vessel? (Assume that none of the water evaporates into the gas phase, so that the only gas present is nitrogen. Also assume that all of the heat from the reaction went into heating the water.)
Note: you will need to use many skills that you learned during this class, such as:
-Determining the formulae of compounds from their names
-Balancing reactions
-Determining limiting reagent
-Using stoichiometry to determined moles of product formed
-Determining the molar enthalpy/heat of a reaction, and then how much heat was actually given off in a specific reaction
-Finding the increase in temperature of a substance given its gain or loss of heat energy
-Determining the pressure of a system of gas
If 43 g of ammonium chloride undergoes a double replacement reaction with 76 g of sodium nitrite, and all the ammonium nitrite that was formed decomposes to nitrogen gas and liquid water in a sealed 0.3 liter flask (originally a vacuum- with no gas) inside a small bomb calorimeter with 400 g water starting at 25.00 degrees C, what becomes the pressure in the vessel? (Assume that none of the water evaporates into the gas phase, so that the only gas present is nitrogen. Also assume that all of the heat from the reaction went into heating the water.) Note: you will need to use many skills that you learned during this class, such as: Determining the formulae of compounds from their names Balancing reactions Determining limiting reagent Using stoichiometry to determined moles of product formed Determining the molar enthalpy/heat of a reaction, and then how much heat was actually given off in a specific reaction Finding the increase in temperature of a substance given its gain or loss of heat energy Determining the pressure of a system of gasExplanation / Answer
Standard enthalpy of formation of:
NH4Cl=-314.55 kJ/mol
H20=-285.8 kJ/mol
NaCl=-407.27 kJ/mol
N2=0
NaNO2= -359.4 kJ/mol
Enthalpy of reaction=(-407.27- 2*285.8) -(-314.55 -359.4)=-304.92 kJ/mol
Heat released=304.92*0.803=244.806 kJ
Total water= (400+1.606*18)=428.908 g
From calorimetry,
mcdT= 244.806
dT =244.806/(428.908*10^-3*4.187)=136.31
Initial T=25+273=298 K
Final T= 298+136.31=434.218
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Finally,
V=0.3 L= 0.3*10^-3 m^3
Number of moles of gases= 1.606 (nitrogen)
T=434.218 K
P=nRT/V =(1.606*8.314*434.218)/(0.3*10^-3)
Pressure=1.93 * 10^-7 Pa