Frequently Asked Question

Here's a step-by-step solution for calculating moles of each substance, along with molar mass calculations:
a) 2.50 g of lead (Pb)

Molar Mass of Pb: The atomic mass of lead (Pb) is 207.2 g/mol.
Calculation:

2.50 g Pb
(1 mol Pb / 207.2 g Pb) = 0.0121 mol Pb

b) 5.00 g of KBr

Molar Mass of KBr:

Potassium (K): 39.10 g/mol

Bromine (Br): 79.90 g/mol

Total: 39.10 + 79.90 = 119.00 g/mol
Calculation:

5.00 g KBr
(1 mol KBr / 119.00 g KBr) = 0.0420 mol KBr

c) 3.75 g of Ca₃(PO₄)₂

Molar Mass of Ca₃(PO₄)₂:

Calcium (Ca): 40.08 g/mol
3 = 120.24 g/mol

Phosphorus (P): 30.97 g/mol
2 = 61.94 g/mol

Oxygen (O): 16.00 g/mol
8 = 128.00 g/mol

Total: 120.24 + 61.94 + 128.00 = 310.18 g/mol
Calculation:

3.75 g Ca₃(PO₄)₂
(1 mol Ca₃(PO₄)₂ / 310.18 g Ca₃(PO₄)₂) = 0.0121 mol Ca₃(PO₄)₂

d) 10.00 g of CH₂CH₂CH₂CH₂CH₂CH₃ (Hexane)

Molar Mass of Hexane:

Carbon (C): 12.01 g/mol
6 = 72.06 g/mol

Hydrogen (H): 1.01 g/mol
14 = 14.14 g/mol

Total: 72.06 + 14.14 = 86.20 g/mol
Calculation:

10.00 g C₆H₁₄
(1 mol C₆H₁₄ / 86.20 g C₆H₁₄) = 0.116 mol C₆H₁₄

e) 15.00 g of CuSO₄·5H₂O (Copper(II) Sulfate Pentahydrate)

Molar Mass of CuSO₄·5H₂O:

Copper (Cu): 63.55 g/mol

Sulfur (S): 32.07 g/mol

Oxygen (O): 16.00 g/mol
9 = 144.00 g/mol

Hydrogen (H): 1.01 g/mol
10 = 10.10 g/mol

Total: 63.55 + 32.07 + 144.00 + 10.10 = 249.72 g/mol
Calculation:

15.00 g CuSO₄·5H₂O
(1 mol CuSO₄·5H₂O / 249.72 g CuSO₄·5H₂O) = 0.0601 mol CuSO₄·5H₂O

f) A cube of copper metal with an edge length of 1.00 in. (Density of copper = 8.92 g/cm³)

Volume of the cube:

1.00 in = 2.54 cm (Conversion from inches to centimeters)

Volume = (2.54 cm)³ = 16.4 cm³
Mass of the cube:

Mass = Density
Volume

Mass = 8.92 g/cm³
16.4 cm³ = 146 g
Molar Mass of Cu: 63.55 g/mol
Calculation:

146 g Cu
(1 mol Cu / 63.55 g Cu) = 2.30 mol Cu