# How to do calculations involving solubility?

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The question I have in my chemistry booklet is:

A student was finding the solubility of sodium chloride in water.

He heated a saturated solution of sodium chloride to dryness, using an evaporating basin.

The following table of results was obtained.

Mass of evaporating basin + sodium chloride solution = 140.57g

Mass of evaporating basin = 72.00 g

So mass of sodium chloride solution = 68.57 g

Mass of evaporating basin + dry sodium chloride = 90.57g

Mass of evaporating basin = 72.00 g

So mass of dry sodium chloride = 18.57 g

1) State the mass of water in the sodium chloride solution.

2) Calculate the solubility of sodium chloride in water in g/100g if water.

I assume that for 1), I must simply subtract 90.57 from 140.57? However, I have no idea how to work out 2). Any input is appreciated!

A student was finding the solubility of sodium chloride in water.

He heated a saturated solution of sodium chloride to dryness, using an evaporating basin.

The following table of results was obtained.

Mass of evaporating basin + sodium chloride solution = 140.57g

Mass of evaporating basin = 72.00 g

So mass of sodium chloride solution = 68.57 g

Mass of evaporating basin + dry sodium chloride = 90.57g

Mass of evaporating basin = 72.00 g

So mass of dry sodium chloride = 18.57 g

1) State the mass of water in the sodium chloride solution.

2) Calculate the solubility of sodium chloride in water in g/100g if water.

I assume that for 1), I must simply subtract 90.57 from 140.57? However, I have no idea how to work out 2). Any input is appreciated!

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(Original post by

The question I have in my chemistry booklet is:

A student was finding the solubility of sodium chloride in water.

He heated a saturated solution of sodium chloride to dryness, using an evaporating basin.

The following table of results was obtained.

Mass of evaporating basin + sodium chloride solution = 140.57g

Mass of evaporating basin = 72.00 g

So mass of sodium chloride solution = 68.57 g

Mass of evaporating basin + dry sodium chloride = 90.57g

Mass of evaporating basin = 72.00 g

So mass of dry sodium chloride = 18.57 g

1) State the mass of water in the sodium chloride solution.

2) Calculate the solubility of sodium chloride in water in g/100g if water.

I assume that for 1), I must simply subtract 90.57 from 140.57? However, I have no idea how to work out 2). Any input is appreciated!

**la95**)The question I have in my chemistry booklet is:

A student was finding the solubility of sodium chloride in water.

He heated a saturated solution of sodium chloride to dryness, using an evaporating basin.

The following table of results was obtained.

Mass of evaporating basin + sodium chloride solution = 140.57g

Mass of evaporating basin = 72.00 g

So mass of sodium chloride solution = 68.57 g

Mass of evaporating basin + dry sodium chloride = 90.57g

Mass of evaporating basin = 72.00 g

So mass of dry sodium chloride = 18.57 g

1) State the mass of water in the sodium chloride solution.

2) Calculate the solubility of sodium chloride in water in g/100g if water.

I assume that for 1), I must simply subtract 90.57 from 140.57? However, I have no idea how to work out 2). Any input is appreciated!

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(Original post by

Well, the solubility in g/100g is simply found by dividing the grams of NaCl in the water you had, by the mass of water. However, you need to make sure that the water is expressed in units of 100g, which would be the mass of water in grams divided by 100 (in this case 0.5).

**PythianLegume**)Well, the solubility in g/100g is simply found by dividing the grams of NaCl in the water you had, by the mass of water. However, you need to make sure that the water is expressed in units of 100g, which would be the mass of water in grams divided by 100 (in this case 0.5).

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(Original post by

Thank you so much for your help! I just wanted to ask for clarification on something (you'll have to bear with me - calculations, even the simplest ones, often go over my head). Why would dividing the mass of water in grams by 100 produce a unit of 100g? I feel silly asking, but I struggle to make such connections!

**la95**)Thank you so much for your help! I just wanted to ask for clarification on something (you'll have to bear with me - calculations, even the simplest ones, often go over my head). Why would dividing the mass of water in grams by 100 produce a unit of 100g? I feel silly asking, but I struggle to make such connections!

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(Original post by

Well think about if it was kg - kg is the same as writing 1000g. To convert from g to kg, you have to divide by 1000. Does that help?

**PythianLegume**)Well think about if it was kg - kg is the same as writing 1000g. To convert from g to kg, you have to divide by 1000. Does that help?

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I'm really struggling with these solubility questions! Does anyone have any idea about this one?

2. A solution of magnesium sulfate is heated to increase solubility and is then cooled. Crystals of hydrated magnesium sulfate are then filtered off and dried. The solubility of hydrated magnesium sulfate at two temperatures is given below.

At 20 degrees C, solubility in g per 100g of water = 36

At 90 degrees C, solubility in g per 100g of water = 123

In a batch process, a saturated solution of magnesium sulfate at 90 degrees C contained 200kg of water. Use the table to calculate the mass of solid hydrated magnesium sulfate crystals produced when the solution was cooled to 20 degrees C.

2. A solution of magnesium sulfate is heated to increase solubility and is then cooled. Crystals of hydrated magnesium sulfate are then filtered off and dried. The solubility of hydrated magnesium sulfate at two temperatures is given below.

At 20 degrees C, solubility in g per 100g of water = 36

At 90 degrees C, solubility in g per 100g of water = 123

In a batch process, a saturated solution of magnesium sulfate at 90 degrees C contained 200kg of water. Use the table to calculate the mass of solid hydrated magnesium sulfate crystals produced when the solution was cooled to 20 degrees C.

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#7

How much gram of magnesium sulfate will precipitate out of every 100g of water?

Once you have that, see if if you can calculate how many grams of the sulfate will precipitate out of 100g of the solution.

Once you have that, see if if you can calculate how many grams of the sulfate will precipitate out of 100g of the solution.

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(Original post by

How much gram of magnesium sulfate will precipitate out of every 100g of water?

Once you have that, see if if you can calculate how many grams of the sulfate will precipitate out of 100g of the solution.

**Borek**)How much gram of magnesium sulfate will precipitate out of every 100g of water?

Once you have that, see if if you can calculate how many grams of the sulfate will precipitate out of 100g of the solution.

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#9

There were 123 g dissolved, now there are 36 g dissolved, how many precipitated out?

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(Original post by

There were 123 g dissolved, now there are 36 g dissolved, how many precipitated out?

**Borek**)There were 123 g dissolved, now there are 36 g dissolved, how many precipitated out?

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