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1. How many moles of the substance are in the following amounts? a) 2.50 g of lead b) 5.00 g of KBr c) 3.75 g of Ca3(PO4)2 d) 10.00 g of CH₂CH₂CH₂CH₂CH₂CH3 e) 15.00 g of CuSO 5 H₂O f) a cube of copper metal with an edge length of 1.00 in. The density of copper is 8.92 g/cm³ solve it srep by step also solve the molar mass and cancel need to be cancel
Accepted Answer
To calculate the number of moles, we'll use the formula: moles = mass (g) / molar mass (g/mol)
Let's break down each part:
a) 2.50 g of lead (Pb)
Molar mass of Pb: 207.2 g/mol
moles: 2.50 g / 207.2 g/mol = 0.0121 mol Pb
b) 5.00 g of KBr
Molar mass of KBr: 39.10 g/mol (K) + 79.90 g/mol (Br) = 119.0 g/mol
moles: 5.00 g / 119.0 g/mol = 0.0420 mol KBr
c) 3.75 g of Ca₃(PO₄)₂
Molar mass of Ca₃(PO₄)₂: (3 x 40.08 g/mol (Ca)) + (2 x 30.97 g/mol (P)) + (8 x 16.00 g/mol (O)) = 310.18 g/mol
moles: 3.75 g / 310.18 g/mol = 0.0121 mol Ca₃(PO₄)₂
d) 10.00 g of CH₂CH₂CH₂CH₂CH₂CH₃ (Hexane)
Molar mass of C₆H₁₄: (6 x 12.01 g/mol (C)) + (14 x 1.01 g/mol (H)) = 86.18 g/mol
moles: 10.00 g / 86.18 g/mol = 0.116 mol C₆H₁₄
e) 15.00 g of CuSO₄·5H₂O (Copper(II) sulfate pentahydrate)
Molar mass of CuSO₄·5H₂O: 63.55 g/mol (Cu) + 32.07 g/mol (S) + (4 x 16.00 g/mol (O)) + (5 x 18.02 g/mol (H₂O)) = 249.69 g/mol
moles: 15.00 g / 249.69 g/mol = 0.0601 mol CuSO₄·5H₂O
f) Cube of copper metal with an edge length of 1.00 in. (Density = 8.92 g/cm³)
Volume of cube: (1.00 in)² = 1.00 in³
Convert volume to cm³: 1.00 in³ x (2.54 cm/in)³ = 16.39 cm³
Mass of cube: 16.39 cm³ x 8.92 g/cm³ = 146.1 g
Molar mass of Cu: 63.55 g/mol
moles: 146.1 g / 63.55 g/mol = 2.30 mol Cu
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