180111

Jan. 18th, 2011 11:15 pm
eternize: dogs (but i give up)
A 0.539g sample of a compound that contained only carbon and hydrogen was subjected to combustion analysis. The combustion produced 1.64g of carbon dioxide and 0.807 g of water. Calculate the percentage composition and teh empirical formula of the sample.

Steps i took:

1. Find moles.
CO2 -> 0.0373moles, H2O -> 0.0448moles

2. Find mass of C and H:
C: 0.448g, H: 0.0905g

3. Find % composition:
C: 83.3%, H: 16.7%

^ this answer is correct, but...

4. Find Empirical formula:

I assume that there are 100g of sample.
So C will be 83.3g and H will be 16.7g. Then i find the number of moles, which is 6.93 (for C) and 16.5 (for H)... And get the smallest ratio which is 1:2, but the book says it's C5H12. ._.?

170110

Jan. 17th, 2011 09:15 pm
eternize: (the surprised gasp)
homologous: structures that share a common origin but may serve different functions in modern society
analogous: structures similar in function but not in origin or anatomical structure

Comparing orca (killer whales) to tiger shark:
Living mostly in water
Possessing structures for swimming
Feeding on fish (often or usually)
Having smooth skin and lacking body hair
Lacking earlobes
Having relatively large size

Comparing orca to bats:
Having lungs to obtain oxygen
Having skeleton comprised of bone
Being warm-blooded
Having a four-chambered heart
Having true bony teeth
Giving birth without laying eggs
Producing milk in mammary glands
Having young that develop internally through placenta


One has to be analogous and one homologous, but idk which one and why. D:
eternize: (looking very smart here)
From Master Mind: The Rise and Fall of Fritz Haber, the Nobel Laureate Who Launched the Age of Chemical Warfare by Daniel Charles.

unfinished, will never be finished )

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krissie。

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