Multiple Choice
Which of the following is the correct chemical formula for potassium hydride?
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3. Chemical Reactions
Naming Ionic Compounds
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Which of the following is the correct chemical formula for cobalt(III) hydroxide?
A
Co(OH)2
B
CoOH
C
Co2(OH)3
D
Co(OH)3
Verified step by step guidance1
Identify the oxidation state of cobalt in cobalt(III) hydroxide. The Roman numeral III indicates that cobalt has a +3 charge, written as Co^{3+}.
Recognize the hydroxide ion, OH^{-}, which has a charge of -1.
To form a neutral compound, the total positive charge from cobalt must balance the total negative charge from hydroxide ions.
Set up the charge balance equation: the charge from cobalt (1 × +3) plus the charge from hydroxide ions (x × -1) must equal zero. This gives +3 + (-1)\times x = 0.
Solve for x, the number of hydroxide ions needed: x = 3. Therefore, the chemical formula is Co(OH)_3.
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