a- Approximately how many grams of KNO3 will dissolve in 100g at 20 degrees C? H

Question

a- Approximately how many grams of KNO3 will dissolve in 100g at 20 degrees C? How many at 60 degrees C?

b- How many grams of KNO3 would dissolve in only 10g of water used at 20 degrees C and 60 degrees C?

c- Approximately how many grams of NaCl will dissolve in 100 grams of water at 20 degrees C? How many at 60?

d- Will there be any visible change in the amount of NaCl that dissolve in a given amount of water as temperature increases from 20 degrees C to 60 degrees C to 100 degrees C?

Explanation / Answer

We are given the solubility curve and using it we can answer the questions.

a) First, we have to look for KNO3.

We know every solute is dissolved in 100 g of H2O. Here we have to look for the amount of KNO3 dissolved at 20 deg C and 60 deg C

At 20-degree C, the amount dissolved would be 35 g approximately.

At 60-degree C, the amount dissolved would be 105 g approximately.

b)

We have to use above information to answer this question.

At 20 deg C , amount of KNO3 dissolved is 35 g per 100 g water and 105 g per 100 g at 60 deg C.

So at 20 deg C for 10 g water, amount of KNO3 dissolved would be

= 10 g H2O x 35.0 g KNO3 / 100 g H2O = 3.5 g KNO3

At 60 deg C

10 g H2O x 105 g KNO3 / 100 g H2O = 10.5 g KNO3

c)

At 20 deg C amount of NaCl dissolved (from the plot of NaCl) is 60 g

At 60 deg C also 60 g.

There is slight change in the dissolution of NaCl but it’s not measurable as we increase the temperature.

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