How many kilojoules are released when 115 g of Si reacts with chlorine?
Si(s)+2Cl2(g)→SiCl4(g)ΔH=−657kJ
dHrxn = (n*dHf products) - (n*dHf reactants) = ?
To determine the number of kilojoules released when 115 g of Si reacts with chlorine, we need to use the given equation and the molar mass of silicon (Si).
Let's begin by calculating the moles of Si.
1. Calculate the molar mass of Si (silicon):
The atomic mass of Si is approximately 28.0855 g/mol.
2. Calculate the moles of Si in 115 g:
moles of Si = mass of Si / molar mass of Si
= 115 g / 28.0855 g/mol
≈ 4.10 mol
According to the balanced equation, 1 mole of Si reacts with 2 moles of Cl2 to form 1 mole of SiCl4. Therefore, since we have 4.10 mol of Si, we can calculate the number of moles of Cl2 that react.
3. Moles of Cl2 = 2 × moles of Si
= 2 × 4.10 mol
= 8.20 mol
Now, we have the moles of Cl2 that react. To determine the amount of kilojoules released, we can use the given enthalpy change (ΔH) value for the reaction.
4. Calculate the kilojoules released:
kilojoules released = ΔH × moles of Si
= -657 kJ × 4.10 mol
≈ -2,692 kJ
Therefore, approximately 2,692 kilojoules are released when 115 g of Si reacts with chlorine.
To determine how many kilojoules (kJ) are released when 115 g of Si reacts with chlorine, we can use the given balanced chemical equation and the energy change associated with the reaction.
First, calculate the molar mass of Si:
- The molar mass of Si is 28.0855 g/mol.
Next, convert the mass of Si given (115 g) to moles:
- Moles of Si = Mass of Si / Molar mass of Si
- Moles of Si = 115 g / 28.0855 g/mol
Now, using the balanced equation, we can determine the stoichiometric ratio between Si and the energy change. From the equation, we can see that 1 mole of Si reacts to produce -657 kJ of energy.
Finally, calculate the energy change (kJ) for the given mass of Si:
- Energy change = Moles of Si * Energy change per mole
- Energy change = (115 g / 28.0855 g/mol) * (-657 kJ/mol)
Performing the calculations, you should find:
- Moles of Si = 4.102 mol (rounded to three decimal places)
- Energy change = (4.102 mol) * (-657 kJ/mol)
- Energy change = -2697.414 kJ (rounded to three decimal places)
Therefore, when 115 g of Si reacts with chlorine, approximately 2697.414 kJ of energy are released.