# 急!!!化學計算題(英文)

what is the empirical formula of the compounds below?

(1) 75%carbon,25%hydrogen

(2)52.7%potassium,47.3%chlorine

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• Anonymous

1. Assume there are 100 g of the compound.

So, mass of carbon = 75 g

Mass of hydrogen = 25 g

Molar mass of carbon = 12.0 g/mol

Molar mass of hydrogen = 1.0 g/mol

By no. of mole = mass / molar mass

No. of mole of carbon

= 75 / 12.0

= 6.25 mol

No. of mole of hydrogen

= 25 / 1.0

= 25.0 mol

So, molar ratio of carbon : hydrogen

= 6.25 : 25.0

= 1 : 4

Therefore, the empirical formula is CH4.

2. Assume there are 100 g of the compound

Mass of potassium = 52.7 g

Mass of chlorine = 47.3 g

Molar mass of potassium = 39.1 g/mol

Molar mass of chlorine = 35.5 g/mol

No. of mole of potassium

= 52.7 / 39.1

= 1.348 mol

No. of mole of chlorine

= 47.3 / 35.5

= 1.332 mol

Molar ratio of potassium : chlorine

= 1.348 : 1.332

~ 1 : 1

So, the empirical formula is KCl.

Source(s): Myself~~~
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• Anonymous

(1) 75ʲbon,25%hydrogen

carbon,　C 分子量 12　　75% 12 x (25%/75%) = 4

hydrogen, H 分子量　1　25% = 4

所以　(1) 75ʲbon,25%hydrogen　＝　CH4

(2)52.7%potassium,47.3%chlorine

potassium, 39.

chlorine 35.5

39 : 35.5 = 52.7% : 47.3 %

所以　52.7%potassium,47.3%chlorine　＝　KCl

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