Chemistry help, advice?

Calculation





Mass of salt = 135.15 - 135.06 = 0.09g





so 25cm3 seawater contains 0.09 g salt


concentration in 1000cm3 seawater =





1000/25 X 0.09g = 3.6 g dm-3





What i dont get is if the calculation to get the concentration is


g dm - 3 = grams(g)/ volume(dm3)


why is the volume times by the grams to get the concentration??





thanksChemistry help, advice?
25 cm鲁 = 0.09 g


10 cm = 1 dm





so...


(0.09 g / 25 cm鲁) x (10 cm / 1 dm)鲁 = 3.6 g / dm鲁





*************


via ';dimensional analysis'; aka ';factor label method';...





read my answer here for an explanation...


http://answers.yahoo.com/question/index;鈥?/a>





************


once you've read that, go back and look at the way I solved this...





(g / cm鲁) x (cm / dm)鲁 ---%26gt; g / dm鲁... the cm鲁 cancels out.





************


I'll say this again for anyone listening. A person onced asked what the most important topic is in chemistry and chemical engineering is. My answer. ';dimensional analysis';.. you learn a process to accurately convert AND you get a head start on the solution to many problems. It is the basis for the math in chemistry and engineering.





*************


questions?Chemistry help, advice?
Use dimensional analysis to work it out.





1,000 cm鲁 = 1 dm鲁, so you have 1,000 cm鲁/dm鲁





The final concentration will be g/dm鲁





So in figures, you have 1000/25 脳 0.09. In units, you have (cm鲁/dm鲁)/cm鲁 脳 g. This works out as cm鲁/dm鲁 脳 1/cm鲁 脳g/1. Cancel the cm鲁, and you will be left with g/dm鲁.





Because the concentration is mass of solute per unit volume of solution, you multiply by the mass.
If there are 0.09g of salt in 25cc, and, there are 1000cc/L (dm鲁), then ...


1000cc / 25cc = 40 times the mass of salt.


There will be 40 x 0.09g in 1.0 litre (dm鲁) = 3.6g/L (dm鲁).

pimples blackheads