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kramer
3 years ago
5

Dolomite is a mixed carbonate of calcium and magnesium that decomposes to CO2 and the metal oxides MgO and CaO upon heating. Whe

n 15.42 g of dolomite is heated, 7.85 g of MgO and CaO are produced. What is percent by mass of MgCO3 in the original sample of dolomite?
Chemistry
1 answer:
kirill [66]3 years ago
7 0

Answer:

47%

Explanation:

MgCO₃ (s) → MgO (s) + CO₂ (g)

CaCO₃ (s) → CaO (s) + CO₂ (g)

_______________________

MgCO₃ (s) + CaCO₃ (s) → MgO (s) + CaO (s) + 2CO₂ (g)

MgO: 40.3044 g/mol

MgCO₃: 84.3139 g/mol

CaO:56.0774 g/mol

CaCO₃: 100.0869 g/mol

CO₂: 44.01 g/mol

15.42 g is the total mass of dolomite.

7.85 g is the sum of MgO and CaO produced.

This means that 7.57 g of CO₂ were produced.

44.01 g CO₂_____ 1 mol

7.57 g CO₂ _____  x

x = 0.172 mol CO₂

Considering the global reaction, we had 0.172/2 = 0.086 mol of MgCO₃ in the original sample.

1 mol MgCO₃ _______ 84.3139 g

0.086 mol MgCO₃ ___ y

y = 7.25 g

15.42 g dolomite ______ 100%

7.25 g MgCO₃ ________ z

z = 47%

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BartSMP [9]

Answer:

330 mL of (NH₄)₂SO₄ are needed

Explanation:

First of all, we determine the reaction:

(NH₄)₂SO₄  +  2NaOH →  2NH₃  +  2H₂O  +  Na₂SO₄

We determine the moles of base:

(First, we convert the volume from mL to L) → 62.6 mL . 1L/1000 mL = 0.0626L

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Ratio is 2:1. Therefore we make a rule of three:

2 moles of hydroxide react with 1 mol of sulfate

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If we want to determine the volume → Moles / Molarity

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We convert from L to mL → 0.330L . 1000 mL/1L = 330 mL

6 0
2 years ago
For a school event 1/6 of the athletic field is reversed for the fifth -grade classes the reserved part of the field is divided
SVETLANKA909090 [29]

Answer:

\frac{1}{24}

Explanation:

Given:

For a school event, 1/6 of the athletic field is reserved for the fifth -grade classes and the reserved part of the field is divided equally among the 4 fifth grade classes in the school.

To find: fraction of the whole athletic field reserved for each fifth class

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3 0
2 years ago
250 mL of a solution of calcium oxalate is the evaporated until only a residue of solid calcium
Lana71 [14]

Answer:

2.3 * 10^-5

Explanation:

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From the question;

1.2 * 10^-3 mols dissolves in 250 mL

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Hence Ksp = [Ca^2+] [C2O4^2-]

Where;

[Ca^2+] = [C2O4^2-] = 4.8 * 10^-3 moldm^-3

Ksp = (4.8 * 10^-3)^2

Ksp = 2.3 * 10^-5

4 0
2 years ago
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laila [671]

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7 0
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