When you make a calibration curve, you need to prepare standard solutions (solutions of known concentration). If you add 5.0 mL of a 2.0 x 10-3 M solution of SCN1- to a 50.0 mL volumetric flask, and dilute to volume, what is the final concentration of SCN1-

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"

let that person have a turn to speak : )