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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
Accepted Answer
To calculate the number of moles, we'll use the formula: moles = mass / molar mass
Here's the breakdown for 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
b) 5.00 g of KBr
Molar mass of KBr = 119.0 g/mol
moles = 5.00 g / 119.0 g/mol = 0.0420 mol
c) 3.75 g of Ca₃(PO₄)₂
Molar mass of Ca₃(PO₄)₂ = 310.18 g/mol
moles = 3.75 g / 310.18 g/mol = 0.0121 mol
d) 10.00 g of CH₂CH₂CH₂CH₂CH₂CH₃ (hexane)
Molar mass of hexane = 86.18 g/mol
moles = 10.00 g / 86.18 g/mol = 0.116 mol
e) 15.00 g of CuSO₄·5H₂O (copper(II) sulfate pentahydrate)
Molar mass of CuSO₄·5H₂O = 249.68 g/mol
moles = 15.00 g / 249.68 g/mol = 0.0601 mol
f) a cube of copper metal with an edge length of 1.00 in.
First, convert inches to centimeters: 1.00 in
2.54 cm/in = 2.54 cm
Calculate the volume of the cube: (2.54 cm)³ = 16.4 cm³
Calculate the mass of the cube: 16.4 cm³
8.92 g/cm³ = 146 g
Calculate the moles: 146 g / 63.55 g/mol = 2.30 mol
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