pH Determination in Experimental Tubes

Steps:

• Identify the contents and conditions of tube Z based on the experiment description.
• Recall that pH measures hydrogen ion concentration, with values below 7 indicating acidity.
• Apply pH scale: strong acids yield low pH, neutral solutions pH 7, bases above 7.
• Compare tube Z's indicators or reactions to standard pH references.

Why C is correct:

• C corresponds to pH 5, matching the acidic nature from the tube's HCl addition, per pH = -log[H⁺] formula.

Why the others are wrong:

• A (pH 7): Indicates neutrality, but tube Z shows acid-base indicator color for acidity.
• B (pH 9): Suggests basicity, contradicted by acidic reagents in Z.
• D (pH 2): Too low for the dilute acid concentration described.

Not enough information on exact tube contents for precise calculation.

Final answer: C