Question

lab 1: acids and bases
complete the chart by indicating the resulting color of these acid - base indicators as they react with an acid and a base.

acid - base indicator	acid (hcl)	base (naoh)
blue litmus paper	(3)	(4)
phenolphthalein	(5)	(6)
methyl orange	(7)	(8)
bromthymol blue	(9)	(10)

complete the chart by indicating whether a noticeable reaction occurs as each substance is placed in a test tube with dilute hydrochloric acid. enter the name of the gas that is liberated from the acid. (if no gas is given off, write none.)

substance	reaction (yes/no)	name of gas
lead	(13)	(14)
copper	(15)	(16)
calcium carbonate	(17)	(18)

fill in the blanks.
(19) acids change the ________ of acid - base indicators.
(20) acids contain hydrogen and react with active metals to produce ________ gas.

Explanation:

Step1: Recall acid-base indicator colors

• Red litmus paper in acid (HCl): remains red (no color change for acid, red litmus is for base detection).
• Red litmus paper in base (NaOH): turns blue.
• Blue litmus paper in acid (HCl): turns red.
• Blue litmus paper in base (NaOH): remains blue.
• Phenolphthalein in acid (HCl): colorless.
• Phenolphthalein in base (NaOH): pink.
• Methyl orange in acid (HCl): red.
• Methyl orange in base (NaOH): yellow.
• Bromthymol blue in acid (HCl): yellow.
• Bromthymol blue in base (NaOH): blue.

Step2: Recall metal-acid reactions (activity series)

• Zinc (Zn) is active, reacts with HCl: \( \text{Zn} + 2\text{HCl}

ightarrow \text{ZnCl}_2 + \text{H}_2 \uparrow \), so reaction: yes, gas: hydrogen.

• Lead (Pb) is active enough (above H in series), reacts: \( \text{Pb} + 2\text{HCl}

ightarrow \text{PbCl}_2 + \text{H}_2 \uparrow \), reaction: yes, gas: hydrogen.

• Copper (Cu) is below H, no reaction: reaction: no, gas: none.
• Calcium carbonate (CaCO₃) with HCl: \( \text{CaCO}_3 + 2\text{HCl}

ightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2 \uparrow \), reaction: yes, gas: carbon dioxide.

Step3: Fill in blanks

• (19) Acids change the color of acid-base indicators.
• (20) Acids react with active metals to produce hydrogen gas.

Answer:

(1) Red; (2) Blue; (3) Red; (4) Blue; (5) Colorless; (6) Pink; (7) Red; (8) Yellow; (9) Yellow; (10) Blue; (11) Yes; (12) Hydrogen; (13) Yes; (14) Hydrogen; (15) No; (16) None; (17) Yes; (18) Carbon Dioxide; (19) Color; (20) Hydrogen