a 2.00g sample of zinc metal is added to a calorimeter containing 150g of nitric acid solution initially at 20.0 degrees celsius . The temperature of the solution increased to 28.0 degrees celsius . Calculate the delta H of the reaction assuming that the specific heat capacity of the solution = 4.18J/g degrees celsius
q = mass x specific heat x delta T.
q = 150 x 4.18 x 8 = ? J which is delta H for the reaction. Most of these problems want delta H/mol or delta H/g but this post asks for neither.
To calculate the delta H of the reaction, we need to use the equation:
delta H = q / n
where delta H is the enthalpy change of the reaction, q is the heat transferred, and n is the number of moles of the substance involved in the reaction.
First, let's calculate the heat transferred in the reaction:
q = mcΔT
where q is the heat transferred, m is the mass of the substance, c is the specific heat capacity of the substance, and ΔT is the change in temperature.
In this case, the substance is the nitric acid solution. We are given the mass of the solution (150g) and the specific heat capacity (4.18 J/g·°C). The change in temperature (ΔT) is the final temperature (28.0°C) minus the initial temperature (20.0°C):
ΔT = 28.0°C - 20.0°C = 8.0°C
Now, we can calculate the heat transferred:
q = (150g)(4.18 J/g·°C)(8.0°C) = 5016 J
Next, we need to calculate the number of moles of zinc metal used in the reaction. We know the mass of the zinc metal (2.00 g) and the molar mass of zinc (65.38 g/mol):
n = m / M
where n is the number of moles, m is the mass, and M is the molar mass.
n = 2.00 g / 65.38 g/mol = 0.0306 mol (rounded to four decimal places)
Finally, we can use the equation:
delta H = q / n
delta H = 5016 J / 0.0306 mol ≈ 163,725 J/mol
The calculated delta H of the reaction is approximately 163,725 J/mol.