Chapter 8: Problem 13
Calculate the molarity of \(\mathrm{Na}^{+}\) ions in each of the following solutions: a. \(0.29 M \mathrm{NaNO}_{3}\) b. \(0.33 \mathrm{g} \mathrm{NaCl}\) in \(25 \mathrm{mL}\) of solution c. \(0.88 M \mathrm{Na}_{2} \mathrm{SO}_{4}\) d. \(0.46 \mathrm{g} \mathrm{Na}_{3} \mathrm{PO}_{4}\) in \(100 \mathrm{mL}\) of solution
Short Answer
Step by step solution
Each formula unit of NaNO3 dissociates into 1 Na+ ion and 1 NO3- ion when dissolved in water. Therefore, there is 1 mole of Na+ ions per mole of NaNO3. #Step 2: Calculate the molarity of Na+ ions#
To find the moles of NaCl, we will use the formula:
The molar mass of NaCl is 58.44 g/mol, so moles of NaCl = 0.33 g / 58.44 g/mol = 0.00565 mol. #Step 2: Calculate the molarity of NaCl#
Molarity = moles / volume (in L)
Since there is 1 mole of Na+ ions per mole of NaCl, the molarity of Na+ ions is also 0.226 M. c. 0.88 M Na2SO4 #Step 1: Identify the number of moles of Na+ ions per mole of Na2SO4#
Since there are 2 moles of Na+ ions per mole of Na2SO4 and the original molarity of Na2SO4 is 0.88 M, the molarity of Na+ ions is 2 * 0.88 M = 1.76 M. d. 0.46 g Na3PO4 in 100 mL of solution #Step 1: Calculate the moles of Na3PO4#
moles = mass / molar mass
To find the molarity, we use the formula:
Since there are 0.002804 moles of Na3PO4 in 0.1 L (100 mL in liters), the molarity of Na3PO4 is: 0.002804 mol / 0.1 L = 0.02804 M. #Step 3: Determine the molarity of Na+ ions#
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Na+ ion concentration
- In \(\mathrm{NaNO}_3\), each molecule contributes 1 \(\mathrm{Na}^+\) ion.
- In \(\mathrm{NaCl}\), each molecule also provides 1 \(\mathrm{Na}^+\) ion.
- For \(\mathrm{Na}_2\mathrm{SO}_4\), each molecule gives 2 \(\mathrm{Na}^+\) ions.
- In \(\mathrm{Na}_3\mathrm{PO}_4\), each molecule generates 3 \(\mathrm{Na}^+\) ions.
Solution chemistry
Important concepts in solution chemistry:
- Dissociation: Ionic compounds separate into ions when dissolved.
- Saturation: The point at which no more solute can dissolve in a solvent at a given temperature.
- Concentration: Measured in molarity, which is moles of solute per liter of solution.
Mole calculations
- First, find the molar mass of the compound (e.g., 58.44 g/mol for \(\mathrm{NaCl}\)).
- Then, use the mass given in the problem to find the number of moles.
- Convert the volume of the solution from mL to L for proper calculations.
Dissolution process
- The water molecules surround the \(\mathrm{NaCl}\) crystals.
- Polar water molecules interact with the \(\mathrm{Na}^+\) and \(\mathrm{Cl}^-\) ions.
- The ions are pulled into the solution, dissociating from each other.
The efficiency of the dissolution process often depends on:
- Temperature: Higher temperatures usually increase solubility.
- Stirring: Helps disperse ions throughout the solution more evenly.
- Nature of the solute and solvent: Polar or nonpolar compounds affect solubility.