送分 ~ 中四 chem 一問

2009-03-22 3:33 am

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Question:

Butane is a fuel that can be found in portale gas containers. The butane gas is liquefied under high pressure. The heat released from the complete combustion of 1 mole of butane is 2877KJ.

Caculate the mass of butane required to boil 1000cm3 of wate from 20C. Stage the assumptions unsed in your calcuations.

( Density of water: 1gm-3, specific heat capactity of water = 4.2 jg-10c-10)

回答 (1)

老爺子

2009-03-22 4:38 pm

✔ 最佳答案

Assumptions:
(1) There is no heat loss to the surroundings. In other words, all energy released in burning of butane is used to heat up the water.
(2) There is no vaporization of water. (The vaporization of water needs latent heat of vaporization.)

Mass of water
= (1000 cm3) x (1 g cm-3)
= 1000 g

Energy absorbed to heat up water
= m c ΔT
= (1000 g) x (4.2 J mol-1 oC-1) x [(100 - 20)oC]
= 336000 J

Energy released by burning of butane
= 336000 J

No. of moles of butane
= (336000 J)/[(2877 kJ mol-1) x (1000 J kJ-1)
= 0.1168 mol

Molar mass of butane
= 12 x 4 + 1 x 10
= 58 g mol-1

Mass of butane
= (0.1168 mol) x (58 g mol-1)
= 6.774 g
=

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