NH4NO3(s) right arrow NH4+(aq) + NO3−(aq)
In order to measure the enthalpy change for this reaction, 1.21 g of NH4NO3 is dissolved in enough water to make 25.0 mL of solution. The initial temperature is 25.8°C and the final temperature (after the solid dissolves) is 22.0°C. Calculate the change in enthalpy for the reaction in kJ. (Use 1.0 g/mL as the density of the solution and 4.18 J/g · °C as the specific heat capacity.)
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
Then delta H/g = q/1.21 and
delta H/mol = (q/1.21) x molar mass NH4NO3. Convert to kJ.
how do I find the mass of H2O?
The problem tells you that the density of h2O is 1.0 g/mL.
mass = volume x density
mass = 25.0 mL x 1.0 g/mL = ? grams.
To calculate the change in enthalpy for this reaction, you will need to use the equation:
q = m * c * ΔT
Where:
q is the heat transferred (in joules)
m is the mass of the solution (in grams)
c is the specific heat capacity of the solution (in J/g · °C)
ΔT is the change in temperature (in °C)
First, let's find the mass of the solution. Since the density of the solution is given as 1.0 g/mL and the volume of the solution is 25.0 mL, the mass of the solution can be calculated as:
mass of solution = density * volume = 1.0 g/mL * 25.0 mL = 25.0 g
Next, we can calculate the change in temperature:
ΔT = final temperature - initial temperature = 22.0°C - 25.8°C = -3.8°C
Now, we can substitute the values into the equation:
q = m * c * ΔT = 25.0 g * 4.18 J/g · °C * -3.8°C = -390.2 J
Note that the value of q obtained is in joules.
To convert the value to kilojoules (kJ), we divide by 1000:
q = -390.2 J / 1000 = -0.3902 kJ
Therefore, the change in enthalpy for the reaction is approximately -0.3902 kJ.