Question

Determine the number of moles of the compound and determine the number of moles of each type of atom in each of the following.

(a)
2.10 g of potassium chloride, KCl
compound WebAssign will check your answer for the correct number of significant figures.
Incorrect: Your answer is incorrect.
mol
K WebAssign will check your answer for the correct number of significant figures.
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mol
Cl WebAssign will check your answer for the correct number of significant figures.
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mol
(b)
0.1410 g of hydrogen(I) phosphate, H3PO4
compound WebAssign will check your answer for the correct number of significant figures.
Incorrect: Your answer is incorrect.
mol
H WebAssign will check your answer for the correct number of significant figures.
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mol
P WebAssign will check your answer for the correct number of significant figures.
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mol
O WebAssign will check your answer for the correct number of significant figures.
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mol
(c)
24.8 kg of magnesium carbonate, MgCO3
compound WebAssign will check your answer for the correct number of significant figures.
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mol
Mg WebAssign will check your answer for the correct number of significant figures.
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mol
C WebAssign will check your answer for the correct number of significant figures.
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mol
O WebAssign will check your answer for the correct number of significant figures.
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mol
(d)
78.36 g of scandium(III) sulfate, Sc2(SO4)3
compound WebAssign will check your answer for the correct number of significant figures.
Incorrect: Your answer is incorrect.
mol
Sc WebAssign will check your answer for the correct number of significant figures.
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mol
S WebAssign will check your answer for the correct number of significant figures.
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mol
O WebAssign will check your answer for the correct number of significant figures.
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mol
(e)
0.1267 mg of xanthine, C5H4N4O2
compound WebAssign will check your answer for the correct number of significant figures. mol
C WebAssign will check your answer for the correct number of significant figures. mol
H WebAssign will check your answer for the correct number of significant figures. mol
N WebAssign will check your answer for the correct number of significant figures. mol
O WebAssign will check your answer for the correct number of significant figures. mol
†

Answer 1

To determine the number of moles of a compound and the number of moles of each type of atom, we need to use the molar masses of the elements and compounds involved. The molar mass is the mass of one mole of a substance and is expressed in grams per mole (g/mol).

Let's calculate the number of moles for each given compound:

(a) Potassium chloride, KCl:

Molar mass of K = 39.10 g/mol

Molar mass of Cl = 35.45 g/mol

To find the number of moles, we use the formula:

Number of moles = Mass of compound / Molar mass

Mass of KCl = 2.10 g

Number of moles of KCl = 2.10 g / (39.10 g/mol + 35.45 g/mol) = 0.0305 mol

Number of moles of K: Since KCl has a 1:1 ratio of K to KCl, the number of moles of K will also be 0.0305 mol.

Number of moles of Cl: Since KCl has a 1:1 ratio of Cl to KCl, the number of moles of Cl will also be 0.0305 mol.

(b) Hydrogen(I) phosphate, H3PO4:

Molar mass of H = 1.01 g/mol

Molar mass of P = 30.97 g/mol

Molar mass of O = 16.00 g/mol

Mass of H3PO4 = 0.1410 g

Number of moles of H3PO4 = 0.1410 g / (3(1.01 g/mol) + 30.97 g/mol + 4(16.00 g/mol)) = 0.00111 mol

Number of moles of H: Since H3PO4 has a 3:1 ratio of H to H3PO4, the number of moles of H will be 3 times the number of moles of H3PO4: 3 * 0.00111 mol = 0.00333 mol.

Number of moles of P: Since H3PO4 has a 1:1 ratio of P to H3PO4, the number of moles of P will also be 0.00111 mol.

Number of moles of O: Since H3PO4 has a 4:1 ratio of O to H3PO4, the number of moles of O will be 4 times the number of moles of H3PO4: 4 * 0.00111 mol = 0.00444 mol.

(c) Magnesium carbonate, MgCO3:

Molar mass of Mg = 24.31 g/mol

Molar mass of C = 12.01 g/mol

Molar mass of O = 16.00 g/mol

Mass of MgCO3 = 24.8 kg = 24,800 g

Number of moles of MgCO3 = 24,800 g / (24.31 g/mol + 12.01 g/mol + 3(16.00 g/mol)) = 399 mol

Number of moles of Mg: Since MgCO3 has a 1:1 ratio of Mg to MgCO3, the number of moles of Mg will also be 399 mol.

Number of moles of C: Since MgCO3 has a 1:1 ratio of C to MgCO3, the number of moles of C will also be 399 mol.

Number of moles of O: Since MgCO3 has a 3:1 ratio of O to Mg