How many kilojoules are released when 130 g of Si reacts with chlorine?
Si(s)+2Cl2(g)→SiCl4(g)ΔH=−657kJ
657 kJ x (130/atomic mass Si) = kJ released.
To determine the amount of kilojoules released when 130 g of Si reacts with chlorine, we can use the given balanced chemical equation and the molar mass of Si.
1. Find the molar mass of Si:
The molar mass of Si is 28.0855 g/mol.
2. Convert the mass of Si to moles:
Moles of Si = Mass (g) / Molar mass (g/mol)
Moles of Si = 130 g / 28.0855 g/mol
Moles of Si ≈ 4.63 mol
3. Use the stoichiometry of the balanced chemical equation to determine the kilojoules released:
According to the balanced chemical equation, 1 mole of Si reacts with 2 moles of Cl2 and releases -657 kJ of energy.
Moles of SiCl4 formed = Moles of Si
Moles of SiCl4 formed ≈ 4.63 mol
Kilojoules released = Moles of SiCl4 formed × ΔH
Kilojoules released = 4.63 mol × (-657 kJ/mol)
Kilojoules released ≈ -3034 kJ
Therefore, approximately 3034 kilojoules are released when 130 g of Si reacts with chlorine.
To find the number of kilojoules released when 130 g of Si reacts with chlorine, you need to use the given enthalpy change (ΔH) and the molar mass of Si.
Here are the steps to calculate it:
1. Determine the molar mass of Si: The molar mass of Si is approximately 28.09 g/mol. This value can be found on the periodic table.
2. Calculate the moles of Si: Divide the given mass of Si (130 g) by the molar mass of Si to get the number of moles.
moles = mass / molar mass
moles of Si = 130 g / 28.09 g/mol
3. Use the balanced chemical equation to determine the stoichiometry: In the balanced equation, 1 mole of Si reacts with 2 moles of Cl2 to produce 1 mole of SiCl4.
4. Calculate the moles of Cl2: Since the stoichiometry is 1:2 (Si:Cl2), the moles of Cl2 will be twice the moles of Si.
moles of Cl2 = 2 * moles of Si
5. Calculate the heat released (in kJ): Multiply the moles of Si by the ΔH value given in the equation.
heat released = moles of Si * ΔH
6. Convert the heat released to kilojoules: Divide the heat released by 1000 to convert it from joules to kilojoules.
heat released in kJ = heat released / 1000
By plugging in the values and following these steps, you can calculate the amount of kilojoules released when 130 g of Si reacts with chlorine.