Reactions of acids and metal hydroxides

Apparatus

• Polystyrene cup

• 250 cm³ beaker

• Thermometer

• 25cm³ measuring cylinder

• Hydrochloric acid

• Sodium hydroxide solution

• Deionised water bottle

Method

1. Place the polystyrene cup into 250 cm³ beaker

2. Add 25cm³ hydrochloric acid into polystyrene cup using measuring cylinder

3. Measure initial temperature and record result

4. Rinse measuring cylinder with deionised water and fill 25cm³ of sodium hydroxide solution

5. Measure temperature of sodium hydroxide solution and record result

6. Add sodium hydroxide solution to acid, stir with thermometer, and measure highest temperature reached during reaction

Observations

• H⁺ ions from acid and OH^- ions from alkali react to form water

• energy is released causing temperature increase on thermometer

• polystyrene cup is good insulator to prevent heat from escaping reaction

Equation

acid + metal hydroxide → salt + water (exothermic)

Error

stir solution thoroughly after to ensure reaction is complete before recording the final temperature (at eye level)

Safety

• safety goggles to protect eyes from splashes

• gloves to protect skin from corrosive chemicals

• handle glassware carefully to avoid breakage

• Work in well-ventilated area