Answer:
pH = 2.21
Explanation:
Hello there!
In this case, according to the reaction between NaF and HCl as the latter is added to the buffer:

It is possible for us to see how more HF is formed as HCl is added and therefore, the capacity of this HF/NaF-buffer is diminished as it turns acid. Therefore, it turns out feasible for us to calculate the consumed moles of NaF and the produced moles of HF due to the change in moles induced by HCl:

Next, we calculate the resulting concentrations to further apply the Henderson-Hasselbach equation:
![[HF]=\frac{0.450mol}{1.0L} =0.450M](https://tex.z-dn.net/?f=%5BHF%5D%3D%5Cfrac%7B0.450mol%7D%7B1.0L%7D%20%3D0.450M)
![[NaF]=\frac{0.050mol}{1.0L} =0.050M](https://tex.z-dn.net/?f=%5BNaF%5D%3D%5Cfrac%7B0.050mol%7D%7B1.0L%7D%20%3D0.050M)
Now, calculated the pKa of HF:

We can proceed to the HH equation:
![pH=pKa+log(\frac{[NaF]}{[HF]} )\\\\pH=3.17+log(\frac{0.05M}{0.45M} )\\\\pH=2.21](https://tex.z-dn.net/?f=pH%3DpKa%2Blog%28%5Cfrac%7B%5BNaF%5D%7D%7B%5BHF%5D%7D%20%29%5C%5C%5C%5CpH%3D3.17%2Blog%28%5Cfrac%7B0.05M%7D%7B0.45M%7D%20%29%5C%5C%5C%5CpH%3D2.21)
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Answer:
Fe₂O₃ is the limiting reactant.
7.57 g of MgO are formed.
Explanation:
- 3 Mg + 1 Fe₂O₃ → 2 Fe + 3 MgO
First we <u>convert the given masses of both reactants into moles</u>, using their <em>respective molar masses</em>:
- 15.6 g Mg ÷ 24.305 g/mol = 0.642 mol Mg
- 10.0 g Fe₂O₃ ÷ 159.69 g/mol = 0.0626 mol Fe₂O₃
0.0626 moles of Fe₂O₃ would react completely with (3 * 0.0626 ) 0.188 moles of Mg. As there are more Mg moles than required, Mg is the reactant in excess; thus, <em>Fe₂O₃ is the limiting reactant</em>.
We now <u>calculate how many MgO moles are produced</u>, using the <em>number of moles of the limiting reactant</em>:
- 0.0626 mol Fe₂O₃ *
= 0.188 mol MgO
Finally we <u>convert moles of MgO into grams</u>:
- 0.188 mol MgO * 40.3 g/mol = 7.57 g
Yes it will ensure that it doesn’t freeze