0.5g of MG ribbon is reacted with 100ml of 1M HCL. The initial temperature of HCL is 20.4 degrees celsius. After the reaction the highest recorded temperature is 40.7 degrees celsius. Calculate the molar enthalpy of MG. I tried to find mol from HCl and then use nH=mcdeltat. Didn't work...
To calculate the molar enthalpy of magnesium (Mg), you need to apply the principles of thermodynamics and stoichiometry. Specifically, you will use the heat gained or lost during the reaction and the stoichiometry of the balanced chemical equation.
Here are the steps to solve the problem:
Step 1: Determine the balanced chemical equation.
The balanced chemical equation for the reaction between magnesium and hydrochloric acid is:
Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)
Step 2: Convert grams of Mg to moles.
Given that you have 0.5 g of Mg, you can calculate the moles of Mg using its molar mass:
Molar mass of Mg = 24.31 g/mol
Moles of Mg = Mass of Mg / Molar mass of Mg
Moles of Mg = 0.5 g / 24.31 g/mol
Step 3: Calculate the amount of heat transferred using the temperature change.
The amount of heat transferred can be calculated using the equation:
q = mcΔT
where q is the heat transferred, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature.
In this case, the heat transferred (q) is equal to the heat absorbed by the reaction. To simplify the calculations, we will assume that the specific heat capacity (c) of the solution is equal to the specific heat capacity of water, which is 4.18 J/(g·°C).
Step 4: Determine the moles of HCl reacted.
The molarity (M) of the hydrochloric acid is provided as 1M, indicating that there is 1 mole of HCl per 1 liter of solution. Since you have 100 ml (0.1 L), you can calculate the moles of HCl:
Moles of HCl = Molarity of HCl × Volume of HCl solution (in liters)
Moles of HCl = 1 mol/L × 0.1 L
Step 5: Use the stoichiometry of the balanced equation to relate the moles of Mg and HCl.
From the balanced equation, you can see that 1 mole of Mg reacts with 2 moles of HCl. Therefore, the moles of Mg reacted can be related to the moles of HCl reacted through the stoichiometry of the reaction.
Step 6: Calculate the molar enthalpy of Mg.
The molar enthalpy (ΔH) of the reaction can be determined by dividing the heat transferred by the moles of Mg reacted.
Now, let's calculate the molar enthalpy of Mg:
1. Calculate the moles of Mg:
Molar mass of Mg = 24.31 g/mol
Moles of Mg = 0.5 g / 24.31 g/mol
2. Calculate the heat transferred using the temperature change:
q = mcΔT
Specific heat capacity (c) = 4.18 J/(g·°C)
Mass used (m) = mass of solution (assume around 100 g) + mass of Mg
ΔT = highest temperature - initial temperature
3. Determine the moles of HCl reacted:
Moles of HCl = Molarity of HCl × Volume of HCl solution (in liters)
Moles of HCl = 1 mol/L × 0.1 L
4. Use the stoichiometry of the balanced equation:
From the balanced equation: 1 mole of Mg reacts with 2 moles of HCl.
Moles of Mg reacted = moles of HCl reacted / 2
5. Calculate the molar enthalpy of Mg:
Molar enthalpy of Mg = heat transferred / moles of Mg reacted
By following these steps and performing the necessary calculations, you will be able to determine the molar enthalpy of magnesium.