How do I dilute 70% ethyl alcohol to 50% into a 200 ml bottle?

Use the dilution formula:

C₁V₁ = C₂V₂

Given:

• Initial concentration (C₁) = 70%
• Final concentration (C₂) = 50%
• Final volume (V₂) = 200 mL

Step 1: Find required volume of 70% alcohol (V₁)

70 × V₁ = 50 × 200

70V₁ = 10000

V₁ = 10000 / 70 = 142.86 mL

Step 2: Find water to add

Water = Final volume − alcohol used

= 200 − 142.86 = 57.14 mL

Final Answer:

• Take 142.86 mL of 70% alcohol
• Add 57.14 mL water to make 200 mL of 50% solution

Key Takeaway:

Use C₁V₁ = C₂V₂ to calculate dilution and then adjust with solvent (water).