Question #76833

1 Answer
Sep 29, 2017

Answer:

#"0.56 h"#

Explanation:

Start by converting the volume of the vessel from liters to milliliters by using the fact that

#color(blue)(ul(color(black)("1 L" = 10^3color(white)(.)"mL")))#

In your case, the vessel contains exactly #"1.0 L"# of water, so you can say that it contains #1.0 * 10^3# #"mL"# of water.

Now, you know that #"1.00 mL"# of water contains #20.0# drops of water. Use this conversion factor to convert the volume of the vessel from milliliters to drops

#1.0 * 10^3 color(red)(cancel(color(black)("mL"))) * "20.0 drops"/(1.00color(red)(cancel(color(black)("mL")))) = 20.0 * 10^3color(white)(.)"drops"#

The problem tells you that you can count the drops at a rate of #"10.0 drops/s"#, so use this conversion factor to find the total time needed to count all the drops present in the vessel

#20.0 * 10^3 color(red)(cancel(color(black)("drops"))) * "1 s"/(10.0color(red)(cancel(color(black)("drops")))) = 2.00 * 10^3color(white)(.)"s"#

Finally, use the fact that

#color(blue)(ul(color(black)("1 h = 3600 s")))#

to convert the time from seconds to hours.

#2.00 * 10^3 color(red)(cancel(color(black)("s"))) * "1 h"/(3600color(red)(cancel(color(black)("s")))) = color(darkgreen)(ul(color(black)("0.56 h")))#

The answer is rounded to two sig figs, the number of sig figs you have for the volume of the vessel.