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.
.109mL times 3.68kJ released for every mL = .40112kJ released by reaction
3.68kJ is given already. It is the amount of energy released per mL
Take the calculated .401kJ and divide by moles of Zn which is mass\molar mass
This gives delta H per mol of Zn
To determine the enthalpy change per mole of zinc for the given reaction, we need to calculate the amount of heat released when 0.0657g of zinc reacts.
First, we need to convert the mass of zinc to moles. To do this, we use the molar mass of zinc (65.38 g/mol):
moles of zinc = mass of zinc / molar mass of zinc
= 0.0657g / 65.38 g/mol
≈ 0.001003 mol
Next, we need to determine the volume of the water/ice mixture. Since the decrease in volume is given as 0.109 mL, we assume that the entire decrease is due to the melting of ice. Thus, the water/ice volume used for the reaction is 0.109 mL.
Now, we can calculate the enthalpy change per mole of zinc using the equation:
enthalpy change = -(heat released / moles of zinc)
To calculate the heat released, we can use the equation:
heat released = mass of water/ice mixture * specific heat capacity of water * temperature change
The specific heat capacity of water is approximately 4.18 J/g°C. The temperature change can be determined by assuming that the reaction caused all the ice to melt and that the heat released was absorbed by the ice/water mixture. The heat absorbed by the ice/water mixture is equal to the heat released by the reaction:
heat released = heat absorbed
Using the equation:
heat absorbed = mass of water/ice mixture * specific heat capacity of water * temperature change
We can rearrange the equation to solve for the temperature change:
temperature change = heat absorbed / (mass of water/ice mixture * specific heat capacity of water)
Given that the density of water is approximately 1 g/mL, the mass of the water/ice mixture can be calculated as:
mass of water/ice mixture = volume of water/ice mixture * density of water
= 0.109 mL * 1 g/mL
= 0.109 g
Let's assume that the specific heat capacity of the water is constant at 4.18 J/g°C. Now, we can calculate the temperature change:
temperature change = heat released / (0.109 g * 4.18 J/g°C)
Next, we need to calculate the heat released using the equation:
heat released = q = mass of zinc * molar enthalpy change
Given that we have 0.001003 mol of zinc and we are trying to find the molar enthalpy change, we can rearrange the equation to solve for the molar enthalpy change:
molar enthalpy change = heat released / moles of zinc
= q / 0.001003 mol
Finally, substitute the calculated values into the equation to find the molar enthalpy change.