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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: XenonX on July 19, 2007, 02:04:43 AM

Title: Pls help me with my quiz questions..
Post by: XenonX on July 19, 2007, 02:04:43 AM

I sat for a quiz yesterday and i would like to have answer for a few questions...

1.Acid attacks limestone to form calcium salts.A piece of limestone weighing 46g reacts completely with 200cm3 of 2.0mol/dm ethanoic acid.What is the percentage purity of the piece of limestone?

PLs show working...

2.What will happen to two blouses each with one drop of oil stain immersed in two beaker filled with well water and distilled water respectively?Pls explain....

Title: Re: Pls help me with my quiz questions..
Post by: AWK on July 19, 2007, 03:01:51 AM

1 Read this link:
http://instructors.butlercc.edu/chemistry/carlson/Chem1labs/lab60.htm

2. nothing

Title: Re: Pls help me with my quiz questions..
Post by: enahs on July 19, 2007, 09:18:10 AM

Those are either some very small blouses or some really big beakers!

Title: Re: Pls help me with my quiz questions..
Post by: XenonX on July 20, 2007, 02:20:02 AM

well..i dun really understand..why there's nothing happen in the two beakers?

Title: Re: Pls help me with my quiz questions..
Post by: AWK on July 20, 2007, 04:14:39 AM

Water does not dissolve an oil

Title: Re: Pls help me with my quiz questions..
Post by: XenonX on July 20, 2007, 07:37:44 AM

not even a distilled water with soap?

Title: Re: Pls help me with my quiz questions..
Post by: AWK on July 20, 2007, 08:10:31 AM

Quote

2.What will happen to two blouses each with one drop of oil stain immersed in two beaker filled with well water and distilled water respectively?Pls explain....

I haven't seen soap here

Title: Re: Pls help me with my quiz questions..
Post by: P on July 20, 2007, 12:22:12 PM

You did not mention soap!    ::)     The hard water lathers less with soap than the soft water - therefore more soap is needed to clean the shirts in the harder water..     I believe this is because the ions in the harder water attract the ions on the surfactant the same way dirt would - thus you need more.

Have a nice weekend!    :)

Title: Re: Pls help me with my quiz questions..
Post by: Yggdrasil on July 20, 2007, 01:34:32 PM

The calcium in hard water forms insoluble salts with the fatty acyl ions in soap, forming a precipitate more commonly known as "soap scum."

Title: Re: Pls help me with my quiz questions..
Post by: XenonX on July 21, 2007, 11:05:54 AM

i am really sorry for missing out the "soap"...anyway...i get confused again as i don't know what is hard water?  And soft water???

Title: Re: Pls help me with my quiz questions..
Post by: Yggdrasil on July 21, 2007, 03:05:38 PM

http://en.wikipedia.org/wiki/Hard_water