i AM HAVING A HARD TIME WITH THIS Here is the question: Calculate the amount of

Question

i AM HAVING A HARD TIME WITH THIS

Here is the question: Calculate the amount of reagent and water requried to make this solution:

400mL of 20mM MgCl2.

IM REALLY STUCK ON TRYING TO FIND THE EXACT NUMERICAL VALUE OF HOW MUCH WATER I NEED TO ADD TO DILUTE!  Here is what I got... I dont know if it is right...

0.4L x 00.02 M MgCL2 x the molecular weight of MgCl2 > 95.2115  = 0.7617 g MgcL2

now... i NEED TO DISSOLVE 0.7617 g of MgCl2 into water and then dilute this to make 400mL solution. How in the world do i figure out exactly how much water to add   how do i get a numerical value? Dont i need to convert 0.7617 into mL to know how much more mL i need to add to make 400 mL????

Explanation / Answer

given 20 milli moles of mgcl2 is to be prepared

we need to prepare 400 ml of 20mm mglcl2

molarity = 20/400 = 0.05 M , so reagent of mglcl2 with a molarity(concentration of) of 0.05 M is required.

water needed = 400 ml as the solvent is water here

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.