Question

Difficulty: MediumSolubility Calculations and Concentration Determination

At 50C50^\circ\text{C}, 21.2 g21.2\text{ g} of anhydrous sodium trioxocarbonate(IV), Na2CO3\text{Na}_2\text{CO}_3, is dissolved in 200 cm3200\text{ cm}^3 of distilled water to form a saturated solution. Calculate the solubility of the salt at this temperature in mol/dm3\text{mol/dm}^3. [Na=23,C=12,O=16][\text{Na} = 23, \text{C} = 12, \text{O} = 16]

Answer:The solubility of Na2CO3\text{Na}_2\text{CO}_3 at 50C50^\circ\text{C} is 【1.00】 mol/dm3\text{mol/dm}^3.

Answer

The solubility of Na2CO3\text{Na}_2\text{CO}_3 at 50C50^\circ\text{C} is 1.00 mol/dm31.00\text{ mol/dm}^3.
To find the solubility in mol/dm3\text{mol/dm}^3, first calculate the molar mass of Na2CO3\text{Na}_2\text{CO}_3: 2(23)+12+3(16)=106 g/mol2(23) + 12 + 3(16) = 106\text{ g/mol}. Next, convert 21.2 g21.2\text{ g} of salt into moles: 21.2/106=0.20 mol21.2 / 106 = 0.20\text{ mol}. Then, convert 200 cm3200\text{ cm}^3 of solvent into dm3\text{dm}^3: 200/1000=0.20 dm3200 / 1000 = 0.20\text{ dm}^3. Dividing moles by volume in dm3\text{dm}^3 gives 0.20/0.20=1.00 mol/dm30.20 / 0.20 = 1.00\text{ mol/dm}^3.

Step-by-Step Solution

1
Calculate the molar mass of Na2CO3\text{Na}_2\text{CO}_3
2(23)+12+3(16)=106 g/mol2(23) + 12 + 3(16) = 106\text{ g/mol}
Molar mass is required to convert mass of solute to moles.
2
Calculate the number of moles of Na2CO3\text{Na}_2\text{CO}_3 dissolved
21.2 g106 g/mol=0.20 mol\frac{21.2\text{ g}}{106\text{ g/mol}} = 0.20\text{ mol}
Determines the mole quantity of solute present in solution.
3
Convert the volume of water from cm3\text{cm}^3 to dm3\text{dm}^3
200 cm31000=0.20 dm3\frac{200\text{ cm}^3}{1000} = 0.20\text{ dm}^3
Solubility in molarity requires volume in cubic decimeters.
4
Calculate solubility in mol/dm3\text{mol/dm}^3
0.20 mol0.20 dm3=1.00 mol/dm3\frac{0.20\text{ mol}}{0.20\text{ dm}^3} = 1.00\text{ mol/dm}^3
Solubility is the number of moles of solute per dm3\text{dm}^3 of solvent.

Key Concept

Solubility Calculation in Moles per Cubic Decimeter
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