Answer:
Procedure (2)
Explanation:
Assume the dialyses come to equilibrium in the allotted times.
Procedure (1)
If you are dialyzing 5 mL of sample against 4 L of water, the concentration of NaCl will be decreased by a factor of

Procedure (2)
For the first dialysis, the factor is

After a second dialysis, the original concentration of NaCl will be reduced by a factor of

Procedure (2) is more efficient by a factor of

Answer: 83%
Explanation:
The detailed solution is shown in the image attached. First we must work out the balanced reaction equation because accurate solution of the problem must be based on the stoichiometry of the reaction. From the given concentration and volume of reactants, we calculate the amount of substance reacted hence identify the limiting reactant. Lastly we use simple proportion to obtain the theoretical yield of the precipitate. This is now used to calculate the actual yield as shown in the solution attached.
B. False. It is banned worldwide for agricultural uses. The <span>use of DDT is still authorized in small proportions in countries that need it, with support deployed for the alteration to safer and more effective alternatives.</span>
Answer: 5.84x10^4
Explanation: You start with (9.00x10^26 atoms)x(1 mol/ 6.022x10^23)x(39.10 g/1 mol)