A nurse wants to add water to 30 ounces of a 10% solution of benzalkonium chloride to dilute it to an 8% solution. How much water must she add?

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Answer 1 · 2016-09-05T19:37:07

7.5 oz

Using the standard dilution equation:

#c_1 * v_1 = c_2 * v_2#

Where:
#c_1# = concentration 1 = 10%
#v_1# = volume 1 = 30 oz
#c_2# = concentration 2 = 8%
#v_2# = volume 2 = ???

Rearranging for #v_2# we get:

#v_2 = (c_1 * v_1) / c_2#

#v_2 = (10 * 30) / 8#

#v_2 = (300) / 8#

#v_2 = 37.5# oz

We already have 30 oz, so just need to add 7.5 oz.

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