Analytical chemistry help?

2017-01-10 6:28 pm

更新1:

Hi could someone please explain how you would work out the following question? A low alcohol beer is found to contain a concentration of ethanol of 500 mg/L, Express this concentration as a % v/v. The density of ethanol is 0.79 g/cm3. Thanks :)

回答 (1)

micatkie

2017-01-10 6:42 pm

The mass of ethanol in 1 L (1000 mL) of the beer
= (1 L) × (500 mg/L)
= 500 mg
= 0.5 g

The volume of ethanol in 1 L (1000 mL) of the beer
= mass / density
= (0.5 g) / (0.79 g/cm³)
= 0.633 cm³

Concentration (% v/v)
= [(0.633 cm³) / (1000 cm³)] × 100%
= 0.0633%

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