Tin metal reacts with hydrogen fluoride to produce tin(II) fluoride and hydrogen gas according to the following balanced equation.
Sn(s)+2HF(g)→SnF2(s)+H2(g)
Sn(s)+2HF(g)→
SnF
2
(s)+
H
2
(g)
How many moles of hydrogen fluoride are required to react completely with 75.0 g of tin?
Step 1: List the known quantities and plan the problem.
Known
given: 75.0 g Sn
molar mass of Sn = 118.69 g/mol
1 mol Sn = 2 mol HF (mole ratio)
Unknown
mol HF
Use the molar mass of Sn to convert the grams of Sn to moles. Then use the mole ratio to convert from mol Sn to mol HF. This will be done in a single two-step calculation.
g Sn → mol Sn → mol HF
Step 2: Solve.
75.0 g Sn×1 mol Sn118.69 g Sn×2 mol HF1 mol Sn=1.26 mol HF
75.0 g Sn×
1
mol Sn
118.69
g Sn
×
2
mol HF
1
mol Sn
=1.26 mol HF
Step 3: Think about your result.
The mass of tin is less than one mole, but the 1:2 ratio means that more than one mole of HF is required for the reaction. The answer has three significant figures because the given mass has three significant figures.
Answer:
pH = 2.66
Explanation:
- Acetic Acid + NaOH → Sodium Acetate + H₂O
First we <u>calculate the number of moles of each reactant</u>, using the <em>given volumes and concentrations</em>:
- 0.75 M Acetic acid * 50.0 mL = 37.5 mmol acetic acid
- 1.0 M NaOH * 10.0 mL = 10 mmol NaOH
We<u> calculate how many acetic acid moles remain after the reaction</u>:
- 37.5 mmol - 10 mmol = 27.5 mmol acetic acid
We now <u>calculate the molar concentration of acetic acid after the reaction</u>:
27.5 mmol / (50.0 mL + 10.0 mL) = 0.458 M
Then we <u>calculate [H⁺]</u>, using the<em> following formula for weak acid solutions</em>:
- [H⁺] =

Finally we <u>calculate the pH</u>:
Answer:3.6 x 101 or 8.77 x 10-1
Answer:
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