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zlopas [31]
3 years ago
5

If 10.57 g of magnesium reacts completely with 6.96 g of oxygen, what is the percent by mass of oxygen in magnesium oxide? Round

to the nearest tenth of a percent.
Chemistry
1 answer:
Deffense [45]3 years ago
5 0

Answer:

39.7 %

Explanation:

magnesium + oxygen ⟶ magnesium oxide

   10.57 g         6.96 g               17.53 g

According to the <em>Law of Conservation of Mass</em>, the mass of the product must equal the total mass of the reactants.

Mass of MgO = 10.57 + 6.96

Mass of MgO = 17.53 g

The formula for mass percent is

% by mass = Mass of component/Total mass × 100 %

In this case,

% O = mass of O/mass of MgO × 100 %

Mass of O = 6.96 g

Mass of MgO = 17.53 g

% O = 6.96/17.53 × 100

% O = 0.3970 × 100

% O = 39.7 %

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An unknown compound, X is thought to have a carboxyl group with a pKa of 2.0 and another ionizable group with a pKa between 5 an
Westkost [7]

Answer:

7.3

Explanation:

By Henderson Hasselbalch equation we can calculate the pH or the pOH of a solution by its pKa. Remember that pH = -log[H^{+}], and pKa = -logKa. Ka is the equilibrium constant of the acid.

Henderson Hasselbalch equation :

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Adding NaOH, with 0.1 mol/L and 75 mL, the number of moles of OH^- will be

n2 = (0.1 mol/L)x(0.075 L) = 0.0075 mol

So, the 0.0075 mol of OH^- reacts with 0.005 mol of carboxyl, remaining 0.0025 mol of OH^-, which will react with the 0.005 mol of the other group. So, it will remain 0.0025 mol of the other group.

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So,

6.72 = pKa - log \frac{0.01}{0.0025}

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8 0
3 years ago
A sample of black coffee was measured to have [h3o+] = 7.94 × 10−6. what is true about this solution?
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Anon25 [30]

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Explanation:

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