Three samples of pure carbon weighing 2,25 g, 4.82 g and 6.11 g were burned.?

2017-07-03 5:31 pm

In each case, complete combustion of the samples produced carbon dioxide only. The masses of carbon dioxide produced were 8.24 g, 17.67 g and 22.40 g, respectively.
A. Do these data establish that carbon dioxide has a fixed composition
B. What is the composition of the carbon dioxide, expressed in percent C and percent O, by mass.

回答 (2)

micatkie

2017-07-03 5:52 pm

✔ 最佳答案

A.
In CO₂ formed from the 2.25-g sample, Mole ratio C : O = 2.25/12 : (8.24-2.25)/16 = 1 : 2
In CO₂ formed from the 4.82-g sample, Mole ratio C : O = 4.82/12 : (17.67-4.82)/16 = 1 : 2
In CO₂ formed from the 6.11-g sample, Mole ratio C : O = 6.11/12 : (22.40-6.11)/16 = 1 : 2
Hence, the carbon dioxide has a fixed composition.
(To show that carbon dioxide has a fixed composition, you can calculate mass ratio of C to O, percent by mass of C or percent by mass of O instead of mole ratio of C to O.)

B.
Mass of C in 1 mole of CO₂ = 12.0 g
Mass of O in 1 mole of CO₂ = 16.0 × 2 g = 32.0 g
Mass of 1 mole of CO₂ = (12.0 + 32.0) g = 44.0 g

In CO₂, percent by mass of C = (12.0/44.0) × 100% = 27.3%
In CO₂, percent by mass of O = (32.0/44.0) × 100% = 72.7%

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[匿名]

2017-07-03 5:43 pm

A. yes

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