•How many grams of solute are needed to prepare: 
•A. 2.50 x 102 g of 5.00% (W/W) NH4Cl
•B. 2.50 x 102 mL of 3.50% (W/V) Na2CO3
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•Calc the amount of water that must be added to 5.00 g of urea (NH2)2CO in the preparation of a 16.2 W/W % by mass solution.