Thomas poured 25 mL of 0.50 M HCl into a large bottle. He then added enough water so that the new (diluted) concentration was 0.10 M HCl. How much water did Thomas add?

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Answer 1 · 2018-04-05T12:51:24

#100# milliliters

Using the dilution equation,

#V_1c_1=V_2c_2#

#V_1,V_2# are the volumes of the two solutions

#c_1,c_2# are the concentrations of the two solutions

So, we get,

#25 \ "mL"*0.5 \ "M"=V_2*0.1 \ "M"#

#V_2=(25 \ "mL"*0.5color(red)cancelcolor(black)"M")/(0.1color(red)cancelcolor(black)"M")#

#=125 \ "mL"#

Since the new volume was #125 \ "mL"#, and the starting volume was #25 \ "mL"#, the amount of water added must be #125 \ "mL"-25 \ "mL"=100 \ "mL"#.