For your recrystallization, you will need to make 75% ethanol in water from 95% ethanol in water. Calculate how much 95% ethanol and water you will need to make 20 mL of 75% ethanol. Hint: You may want to use M1V1=M2V2.

15.79 mL of ethanol and 4.21 mL of water

Explanation:

Initial concentration of ethanol = 95%

Final concentration of ethanol (to be prepared) = 75%

Initial volume of ethanol to be taken = ?

Final volume of ethanol to be prepared = 20 ml

Using the dilution equation: M1V1 = M2V2, where;

M1 = initial concentration = 95%

V1 = initial volume = ?

M2 = final concentration = 75%

V2 = final volume = 20 mL

Substitute each value in the equation:

95 x (initial volume) = 75 x 20

Initial volume = 75 x 20/95

                        = 15.79 mL

The volume of 95% ethanol to be taken is 15.79 mL.

In order to calculate the volume of water need, subtract the initial ethanol volume from the final volume of solution to be prepared.

   20 - 15.79 = 4.21 mL

Hence, 15.79 mL of 95% ethanol and 4.21 mL of water will be needed to make 20 mL of 75% ethanol.

answer: option (4) is the correct answer.

explanation:

areas which are at low altitudes and near the equator tend to receive direct sunlight from the sun. hence, heat energy or radiations from the sun make these areas warmer and they have warmest water.

whereas areas which are at high altitudes and away from the equator do no receive direct sunlight. hence, no direct contact from the sun makes these regions colder and thus, they have colder water.

thus, we can conclude that the statement areas at low latitudes near the equator have the warmest water because they receive the most direct sunlight best explains the relationship between an area's geography and the temperature of its surface water.