Zinc dissolves in acid according to the balanced equation.
Zn(s)+ 2H(aq)-> Zn(aq) + H2(g)
a sample of zinc is placed in a ice calorimeter. If 0.0657g of zinc causes a decrease of 0.109ml in the ice/water volume of the calorimeter, what is the enthalpy change, per mole of zinc, for the above reaction per mole of zinc.
To determine the enthalpy change per mole of zinc for the given reaction, we need to calculate the amount of heat absorbed by the calorimeter.
First, we need to convert the mass of zinc from grams to moles. The molar mass of zinc (Zn) is approximately 65.38 g/mol. Therefore, the number of moles of zinc is:
(0.0657 g) / (65.38 g/mol) = 0.00100 mol
Next, we need to calculate the change in volume of the ice/water in the calorimeter. The decrease in volume is given as 0.109 mL.
Now, we can use the formula:
q = m × ΔT
where q is the heat absorbed or released by the system, m is the mass of the substance, and ΔT is the change in temperature.
In this case, the ice/water mixture in the calorimeter acts as the system, and the heat is absorbed as the reaction proceeds.
However, since we are using an ice calorimeter, we assume that the temperature remains constant during the reaction. Therefore, the change in temperature (ΔT) is zero.
q = 0.109 mL × 1 g/mL × 0 K = 0 J
The change in heat (q) is zero since there is no change in temperature.
Next, we need to calculate the enthalpy change (ΔH) for the reaction per mole of zinc. Since ΔH is given by q/n, where n is the number of moles, we can calculate:
ΔH = 0 J / 0.00100 mol = 0 J/mol
Therefore, the enthalpy change per mole of zinc for the given reaction is 0 J/mol.
To calculate the enthalpy change per mole of zinc for the given reaction, we need to use the equation:
ΔH = q / n
Where:
ΔH is the enthalpy change
q is the heat gained or lost
n is the amount of substance (in moles)
First, we need to calculate the heat gained or lost by the system (q). We can use the equation:
q = m × c × ΔT
Where:
m is the mass of the solution in grams
c is the specific heat capacity of the solution (assumed to be the same as water, which is 4.184 J/g°C)
ΔT is the change in temperature in °C
The ice/water volume decreased by 0.109 mL, which means that the mass of the solution is 0.109 g (since the density of water is approximately 1 g/mL). The change in temperature (ΔT) is assumed to be 0 since the system is kept at constant temperature in an ice calorimeter.
Using the equation:
q = (0.109 g) × (4.184 J/g°C) × (0 °C) = 0 J
Since there is no temperature change, there is no heat gained or lost by the system (q = 0 J).
Now, we need to calculate the number of moles of zinc used in the reaction. The molar mass of zinc (Zn) is 65.38 g/mol.
n = mass / molar mass
n = 0.0657 g / 65.38 g/mol = 0.001 mol
Finally, we can calculate the enthalpy change per mole of zinc:
ΔH = q / n
ΔH = 0 J / 0.001 mol = 0 J/mol
Therefore, the enthalpy change per mole of zinc for the given reaction is 0 J/mol.