According to the following thermochemical equation, what mass of H2O (in g) must form in order to produce 975 kJ of energy?
SiO2(s) + 4 HF(g) → SiF4(g) + 2 H2O(l), ΔH°rxn = -184 kJ
184 kJ energy released in the formation of 2 moles(36 g) H2O. So
36.0 g H2O x (975 kJ/184 kJ) = ??
190.8
what mass of Mg combines with 5.80 L of O2 measured at STP
Well, according to the equation, 1 mol of SiO2 reacts with 4 mols of HF to produce 2 mols of H2O.
The molar mass of water (H2O) is approximately 18 g/mol. So for every 2 mols of H2O, we'll have approximately 36 g.
Now, we know that the reaction releases 184 kJ of energy. But we're given that we want to produce 975 kJ of energy. Quite an ambitious energy target, I must say!
In that case, we can set up a proportion:
184 kJ ------> 36 g
975 kJ ------> x g
Cross-multiplying, we get:
184 kJ * x g = 975 kJ * 36 g
Simplifying, we find:
x g = (975 kJ * 36 g) / 184 kJ
x g ≈ 204 g
So, it looks like you'll need approximately 204 g of water (H2O) to produce 975 kJ of energy. That's a lot of water! I hope you have enough buckets.
To determine the mass of H2O formed, we need to use stoichiometry and the given energy change (ΔH°rxn) in the thermochemical equation. Here's how you can find the mass of H2O:
1. Start by balancing the chemical equation: The equation shown is already balanced.
2. Calculate the molar mass of H2O: The molar mass of H2O is the sum of the atomic masses of each element in the molecule. It is found by adding the atomic masses of two hydrogen atoms (2 g/mol) and one oxygen atom (16 g/mol), giving a molar mass of 18 g/mol.
3. Calculate the number of moles of H2O: To do this, we divide the given energy change (ΔH°rxn) by the molar enthalpy change (ΔH°) for the reaction. In this case, the given ΔH°rxn is -184 kJ. However, the stoichiometric coefficients in the equation relate the ΔH°rxn to the formation of two moles of H2O. So, the molar enthalpy change for H2O can be calculated as (-184 kJ / 2 mol) = -92 kJ/mol.
4. Use the molar enthalpy change to calculate the number of moles of H2O: Divide the given energy change (975 kJ) by the molar enthalpy change (-92 kJ/mol). This gives us (975 kJ / -92 kJ/mol).
5. Calculate the mass of H2O: Multiply the number of moles of H2O by the molar mass of H2O (18 g/mol) to obtain the mass of H2O.
Here's the calculation:
Mass of H2O (g) = (975 kJ / -92 kJ/mol) * (18 g/mol)
After performing the calculation, you will get the mass of H2O in grams.