Answer:
3 mol Cl₂/2 mol AlCl₃ (three over two)
Step-by-step explanation:
Start with the balanced equation"
2Al + 3Cl₂⟶ 2AlCl₃
The steps in the calculation are
mass of AlCl₃ ⟶ moles of AlCl₃⟶ moles of Cl₂ ⟶ mass of Cl₂
The critical step is the <em>conversion of moles</em>.
You multiply the moles of AlCl₃ by a <em>conversion factor</em> to get moles of Al:
Moles of AlCl₃ × conversion factor = moles of Al.
The conversion factor is <em>the molar ratio</em>, and it uses the coefficients of the formulas in the balanced equation.
It is either (2 mol AlCl₃/3 mol Cl₂) or (3 mol Cl₂/2 mol AlCl₃).
You choose the one that has the desired units of the answer in the numerator.
We choose the second option, because it has the correct units.
For example,
Notice how the units "mol AlCl₃" cancel and the correct units appear in the answer.
If we had used the other conversion factor, we would have gotten the wrong units.
The number of moles in a substance may be calculated using:
Moles = mass / molecular mass
The molecular mass of CH₂Cl₂ is:
12 + 2 * 1 + 2 * 35.5
= 85 grams / mole
Moles = 76.1 / 85
Moles = 0.895
There are 0.90 moles of CH₂Cl₂ present in 76.1 grams.
<h3>
Answer: Choice A) 0-7</h3>
Explanation:
If the pH is between 0 and 7, then we have an acid.
If the pH is between 7 and 14, then we have an alkaline base.
If pH = 7, then it's neutral.
A pseudoscientific theory
Answer:
0.20 moles of Pb(CH3COO)4
Explanation:
89g Pb(CH3COO)4 x 1 mol Pb(CH3COO)4 / 443.376 g Pb(CH3COO)4
= 0.20 moles of Pb(CH3COO)4