2010 Chemistry qn20 mc (1 Viewer)

[forthehsc]

can someone explain how we're meant to do qn20, i dont really undertsand ppm

 

[b3kh1t]

can someone explain how we're meant to do qn20, i dont really undertsand ppm

ppm is basically the same as mg/L, where 1000 mg = 1 g. If you want to another example look here http://community.boredofstudies.org/showthread.php?t=270087, and if you still need help just say the answer to the question is as follows.

As the curve will be linear or close to it, we can say
which equals 12.5 mg/L

the amount of Cu2+ in 100 mL is 1/10x12.5=1.25 mg
therefore the number of moles of Cu2+= 0.00125/65.55 = 1.97x10^-5 moles



It can be seen that number of moles of Cu2+ = number of moles of CuCO3
therefore number of moles of CuCO3 = 1.97x10^-5
therefore mass of CuCO3 = 1.97x10^-5 x 123.55 = 2.43x10^-3g

therefore answer is (B)