Multiple Choice
Which of the following numerical expressions gives the number of moles in a sample containing mass m (in grams) of a substance with molar mass M (in g/mol)?
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2. Atoms & Elements
Mole Concept
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How many atoms of Mg, O, and H are present in 3 formula units of Mg(OH)_2?
A
3 Mg atoms, 6 O atoms, and 6 H atoms
B
6 Mg atoms, 3 O atoms, and 6 H atoms
C
3 Mg atoms, 3 O atoms, and 6 H atoms
D
6 Mg atoms, 6 O atoms, and 3 H atoms
Verified step by step guidance1
Identify the number of each type of atom in one formula unit of Mg(OH)\(_2\). In one formula unit, there is 1 Mg atom, 2 O atoms (from the two OH groups), and 2 H atoms (also from the two OH groups).
Write down the composition per formula unit: 1 Mg, 2 O, and 2 H atoms.
Multiply the number of atoms of each element by the number of formula units given, which is 3 in this problem.
Calculate the total atoms for each element: Total Mg atoms = \$1 \times 3\(, Total O atoms = \)2 \times 3\(, Total H atoms = \)2 \times 3$.
Summarize the results to find the total number of Mg, O, and H atoms present in 3 formula units of Mg(OH)\(_2\).
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