How many grams of Zinc will react with 25 mL of a 4.0 M HCl solution to produce Hydrogen gas? 2HCl + Zn --> ZnCl2 + H2

Answer 1

Complete Dimensional Analysis

25 mL x (1L/1000 mL) x (4 mol HCl/1L) x (1 mol Zn/2 mol HCl) x (65.38 g Zn/1 mol Zn) = 3.269g = ~ 3.3g of Zn

Parts explained

25 mL x (1L/1000 mL) x (4 mol HCl/1L) = 0.1 mol of HCl that reacts with Zn. Note: (1L/1000mL) is conversion factor to change mL to L

25 mL x (1L/1000 mL) x (4 mol HCl/1L) x (1 mol Zn/2 mol HCl) = 0.05 mol of Zn that reacts completely with 0.1 mol of HCl. Note: From the balanced equation, 2 mol of HCl reacts with 1 mol Zn, thus we use (1 mol Zn/2 mol HCl) as conversion factor

(65.38 g Zn/1 mol Zn) = Molar mass of Zn, used to convert moles to grams.

Answer 2

25 mL*1 L/1000. mL=0.025 L. This is your volume of HCl in liters.

0.025L*4.0 mol HCl/L=0.10 mol HCl. This is the number of moles of HCl.

0.10 mol HCl*1 mol Zn/2 mol HCl=0.050 mol Zn. This is the number of moles of Zn.

0.050 mol Zn*65.38 g/mol Zn=3.3 g Zn. This is your mass of Zn.