The accepted value for the enthalpy for the following reaction reaction is 466.85 kJ/mol.
Mg + 2Hcl = MgCl2 + H2
Calculate the heat that would be generated if 5.00g of magnesium reacts with excess hydrochloric acid.
I don't even know how to start this problem, please help
To calculate the heat generated in a chemical reaction, you need to use the equation:
q = m * C * ΔT
where:
q = heat (in joules)
m = mass (in grams)
C = specific heat capacity of the substance (in J/g°C)
ΔT = change in temperature (in °C)
In this case, we have the equation:
Mg + 2HCl → MgCl2 + H2
First, let's calculate the moles of magnesium (Mg) using the given mass:
Given: mass of magnesium (Mg) = 5.00g
Atomic mass of magnesium (Mg) = 24.31 g/mol
moles of Mg = mass of Mg (g) / atomic mass of Mg (g/mol)
= 5.00g / 24.31 g/mol
Now, let's look at the stoichiometry of the reaction. From the balanced equation, we can see that 1 mole of Mg reacts with 2 moles of HCl.
So, the moles of HCl = 2 * moles of Mg
Once you find the moles of HCl, you can calculate the heat generated using the equation mentioned earlier.
Now, we need to convert the moles of HCl to grams, using the molar mass of hydrochloric acid:
Molar mass of HCl (hydrochloric acid) = 36.46 g/mol
mass of HCl = moles of HCl * molar mass of HCl
Considering that hydrochloric acid is present in excess, all the moles of HCl react with magnesium. Therefore, you can calculate the heat generated using the equation:
q = ΔH * moles of Mg
where ΔH is the enthalpy change for the reaction.
Given that the accepted value for the enthalpy change of the reaction is 466.85 kJ/mol, you need to convert it to joules by multiplying by 1000:
ΔH = 466.85 kJ/mol * 1000 J/kJ
Now, substitute the values into the equation q = ΔH * moles of Mg to calculate the heat generated.
Reason it out. Use the equation. That tells you that 1 mol Mg (that's 24.3 grams Mg) evolves 466.85 kJ. So what will 5.00 g Mg evolve? You can set up a ratio/proportion or use
466.85 kJ x (5.00 g/24.3g) = ? kJ.
The ratio/proportion looks like this.
(5.00/24.3) = (x kJ/466.85 kJ)