Multiple Choice
Which of the following is the correct chemical formula for the ionic compound rubidium cyanide?
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3. Chemical Reactions
Writing Ionic Compounds
Multiple Choice
Which of the following is the correct chemical formula for the compound aluminum sulfide?
A
Al2S3
B
AlS
C
Al3S2
D
AlS3
Verified step by step guidance1
Identify the charges of the ions involved: aluminum typically forms a +3 charge (Al^{3+}), and sulfide forms a -2 charge (S^{2-}).
Determine the ratio of aluminum ions to sulfide ions needed to balance the overall charge to zero.
Use the crisscross method to balance the charges: the charge magnitude of aluminum (3) becomes the subscript for sulfur, and the charge magnitude of sulfur (2) becomes the subscript for aluminum.
Write the chemical formula using the subscripts found: Al with subscript 2 and S with subscript 3, resulting in Al_{2}S_{3}.
Verify that the total positive charge from aluminum ions (+3 × 2 = +6) balances the total negative charge from sulfide ions (-2 × 3 = -6), confirming the formula is electrically neutral.
