Question

What volume of 5.00 x 10 - 2 mol/L Ca(NO3)2 solution will contain 2.50 x 10 - 2 mol of nitrate ions?Select one:a.200 mLb.250 mLc.500 mLd.750 mL

Answer 1

The answer is b 250 ml

Answer 2

The first step to answer this question is to find the number of moles of Ca(NO3)2 that contain 2.50x10^-2 moles of nitrate ion. According to the chemical formula of Ca(NO3)2, there are 2 moles of nitrate ions per mol of Ca(NO3)2:

`2.50*10^(-2)molNO_3^-\cdot(1molCa(NO_3)_2)/(2molNO_3^-)=1.25*10^(-2)molCa(NO_3)_2`

The next step is to use the concentration of the Ca(NO3)2 solution to find the volume that contains this number of moles:

`1.25*10^(-2)molCa(NO_3)_2\cdot(1L)/(5.00*10^(-2)molCa(NO_3)_2)=0.25L`

Finally, convert this volume to mL:

`0.25L\cdot(1000mL)/(L)=250mL`

It means that the correct answer is b. 250mL.