The answer for this question is ΔHrxn=-441.40174468085 kJ/mol but I don't know how to arrive to that answer.
0.47g of magnesium reacts with 100ml of 1.00 mol/L HCl in the following reaction: Mg(s)+2HCl(aq)-->MgCl2(aq)+H2(g). The heat of reaction is -8537.4J
Determine ΔHrxn.
qrxn is -8537.4 J
q/gram = -8537.4/0.47 = ?
q/mol = -8537.4/0.47g)*(24.3 g/mol) x (1 kJ/1000 J) = -441.4017 kJ/mol but if that 0.47 g Mg is correct you're allowed only two significant figures.
To solve this problem and find ΔHrxn, we need to use the given information and apply the appropriate formula.
The first step is to convert the mass of magnesium into moles. We can do this by dividing the mass of magnesium by its molar mass. The molar mass of magnesium is 24.31 g/mol, so:
0.47 g / 24.31 g/mol = 0.01933 mol
Next, we need to determine the number of moles of HCl in the solution. We can do this by using the formula:
moles = concentration × volume
Given that the concentration of HCl is 1.00 mol/L and the volume is 100 ml (or 0.100 L), we have:
moles = 1.00 mol/L × 0.100 L = 0.100 mol
The stoichiometry of the balanced equation tells us that 1 mol of magnesium reacts with 2 moles of HCl. Since we have 0.01933 mol of magnesium, we will need:
0.01933 mol Mg × 2 mol HCl/mol Mg = 0.03866 mol HCl
The ΔHrxn is given as -8537.4 J. However, the answer should be in kJ/mol, so we need to convert this value to kJ. Since 1 J = 0.001 kJ, we have:
-8537.4 J × 0.001 kJ/J = -8.5374 kJ
Finally, to determine ΔHrxn, we need to calculate the heat of reaction per mole of magnesium. We can use the equation:
ΔHrxn = heat of reaction (in kJ) / number of moles of magnesium
ΔHrxn = -8.5374 kJ / 0.01933 mol = -441.40174468085 kJ/mol
Therefore, the ΔHrxn for the given reaction is -441.40174468085 kJ/mol.