Hydrogen sulfide gas is bubbled through an excess of potassium hydroxide solution.

Hydrogen sulfide gas is bubbled through an excess of potassium hydroxide solution. H2S + 2OH- → S2- + 2H2O Write the balanced chemical equation excluding spectator ions. How do you get there from H2S + KOH -> K2S + H2O?

The correct Answer and Explanation is:

Initial understanding:

• Hydrogen sulfide (H₂S) reacts with potassium hydroxide (KOH) to produce potassium sulfide (K₂S) and water (H₂O).
• The given simplified unbalanced reaction is:
  H₂S + KOH → K₂S + H₂O

Step 1: Write the unbalanced skeletal equation

H2S+KOH→K2S+H2OH2​S+KOH→K2​S+H2​O

Step 2: Balance potassium (K) atoms

• On the right, K₂S contains 2 K atoms.
• On the left, potassium appears only in KOH. To supply 2 K atoms, we need 2 KOH molecules.

H2S+2 KOH→K2S+H2OH2​S+2KOH→K2​S+H2​O

Step 3: Check sulfur and hydrogen atoms

• Sulfur: 1 S on both sides.
• Hydrogen: 2 H in H₂S, and 2 H in 2 KOH (since each KOH has 1 H). On the product side, water has 2 H, matching the total H on the reactant side.

Step 4: Confirm the oxygen atoms

• Left: 2 KOH molecules contribute 2 O atoms.
• Right: 1 H₂O molecule has 1 O atom.

This shows an imbalance in oxygen atoms. To balance oxygen, the product side should have 2 water molecules (since total O on reactant side is 2). So, update the product side:

H2S+2 KOH→K2S+2 H2OH2​S+2KOH→K2​S+2H2​O

Now, oxygen atoms are balanced: 2 on each side.

Final balanced chemical equation:

H2S+2 KOH→K2S+2 H2OH2​S+2KOH→K2​S+2H2​O

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Explanation of the derivation:

This balanced chemical equation is consistent with the initial reaction of hydrogen sulfide with potassium hydroxide. The key steps involve:

• Recognizing that 2 KOH molecules are needed to supply enough potassium ions (K⁺) to form potassium sulfide (K₂S).
• Ensuring sulfur atoms are balanced: 1 S on each side.
• Balancing hydrogen atoms: 2 H from H₂S and 2 H from 2 KOH, resulting in 2 water molecules.
• Balancing oxygen atoms: both sides have 2 oxygen atoms.

Important note:
The initial chemical equation involving spectator ions, H₂S + 2OH⁻ → S²⁻ + 2H₂O, is a net ionic form, focusing on the actual reacting species (hydroxide ions and H₂S). When considering the full molecular reaction with potassium ions, the balanced molecular equation includes KOH as shown above.

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Summary:
Starting from the unbalanced reaction, by balancing K, H, and O atoms, we arrive at the balanced molecular equation:

H2S+2 KOH→K2S+2 H2OH2​S+2KOH→K2​S+2H2​O​