Chapter 1: 1.13. (page 8)

A mole is approximately the number of protons in a gram of protons. The mass of a neutron is about the same as the mass of a proton, while the mass of an electron is usually negligible in comparison, so if you know the total number of protons and neutrons in a molecule(i,e., its "atomic mass"), you know the approximate mass(in grams) of a mole of these molecules. Referring to the periodic table at the back of this book ,find the mass of a mole of each of the following : Water, nitrogen (N₂), lead, quartz (S_i O₂)

Expert verified

18g, 28g, 207.2g, 60g

Step by step solution

Water consists of 2 hydrogen atoms & 1 oxygen atom, Hence, $m_{H_{2} O =} 2 m_{H} + 1 m_{o}$

Using the concept, hydrogen has 1g of atomic weight and oxygen has 16g of atomic weight

m_H_2O=2(1)+1(16)

m_H_2O=18g

Nitrogen has 2 nitrogen atoms

$m_{N_{2}} = 2 m_{N}$

$m_{N_{2}} = 2 (14) = 28 g$

Lead has 1Pb atom

m_pb=1m_pb= 1(207.2)=207.2g

SiO₂ has 1 silicon atom and 2 oxygen atoms

$m_{S i O_{2}} = 1 m_{s i} + 2 m_{o} m_{S i O_{2}} = 1 (28) + 2 (16) = 60 g$

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