Question

In a coffee cup calorimeter, 12.0 g of zinc (Zn) are reacted with 0.5 L of 0.8 molars (M) HCl . The temperature of the water increases from 25.0 °C to 31.9 °C. If the HCl solution has a density of 1.0 g/mL, what is the (in kilojoules per mole)? Zn(s) + 2HCl(aq) → H(g) + ZnCl(aq)

Answer 1

The enthalpy change per mole of zinc can be calculated using the heat capacity formula with the given masses, temperature change, and density. The energy absorbed by the HCl solution is divided by the moles of zinc to find the enthalpy change per mole.

Step-by-step explanation:

Calculating the Enthalpy Change per Mole of Zinc

To calculate the enthalpy change per mole of zinc, we have to use the data provided for the reaction of zinc with hydrochloric acid in a coffee cup calorimeter. We need to know the mass of the zinc, the volume and concentration of the HCl used, the temperature change of the solution, and the density of the HCl solution.

First, calculate the total heat absorbed using the formula q = mcΔT, where m is the mass of the HCl solution, c is the specific heat capacity (we will assume the specific heat capacity of water, which is 4.18 J/g°C), and ΔT is the change in temperature. Using the density of HCl, we can find the mass of 0.5 L of HCl solution is 500 g. The temperature change is from 25.0°C to 31.9°C, so ΔT = 6.9°C.

The heat absorbed by the solution, q, is then calculated and converted to kilojoules. Next, we need to determine the number of moles of zinc reacted. From the mass of zinc provided, we can use zinc's molar mass to find the number of moles. Lastly, we divide the total absorbed heat by the number of moles of zinc to find the enthalpy change per mole (ΔH).

Remember, this calculation assumes that all the heat absorbed by the solution is due to the reaction of zinc, and that the calorimeter does not absorb any heat itself. Additionally, the calculation assumes the specific heat capacity of the water-based solution is the same as that of pure water.

Answer 2

To find the enthalpy change per mole of zinc in the calorimeter, calculate the heat absorbed based on the mass of the solution and temperature change, then divide by the moles of zinc reacted.

Step-by-step explanation:

To calculate the enthalpy change per mole of zinc reacting in the coffee cup calorimeter, we first need to determine the amount of heat absorbed by the solution. We know the mass of zinc, the volume and molarity of HCl, and the temperature change.

Use the formula q = mcΔT, where q is the heat absorbed by the solution, m is the mass of the solution, c is the specific heat capacity (for water, c = 4.184 J/g°C), and ΔT is the change in temperature.

The mass of the HCl solution can be calculated since the density is given as 1.0 g/mL. With 0.5 L (or 500 mL) of solution, the mass is 500 g. The temperature increased by 6.9°C (31.9°C - 25.0°C). Plugging these values into the formula gives us the heat absorbed by the solution.

To find the enthalpy change per mole, we then divide the heat (q) by the number of moles of Zn that reacted. The molar mass of Zn is approximately 65.38 g/mol. With 12.0 g of Zn, we can calculate the moles of Zn and use it to find the enthalpy change per mole.