How would you prepare 100.0 mL of 0.400 M CaCl2 from a stock solution of 2.00 M CaCl2?

Measure 20mL of the stock

Explanation:

All we need to do is to find the volume of the stock solution needed. This is illustrated below:

C1 = 2M

V1 =?

C2 = 0.400 M

V2 = 100mL

C1V1 = C2V2

2 x V1 = 0.4 x 100

Divide both side by 2

V1 = ( 0.4 x 100) /2

V1 = 20mL

Therefore, to prepare the solution, we will measure 20mL of the stock solution and make it up to the 100mL mark.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.