Molar mass of NaCl is 58.44 g/mol (this means, 1 mole of NaCl weighs 58.44 g). You are a researcher who needs to prepare several solutions. How many grams of NaCl do you need to take to prepare: a) 1 L of 1 M solution of NaCl? b) 1 L of 0.5 M solution of NaCl?
The Correct Answer and Explanation is:
To calculate the mass of NaCl needed to prepare solutions of specific molarity, we use the formula:Mass (g)=Molarity (mol/L)×Volume (L)×Molar Mass (g/mol)\text{Mass (g)} = \text{Molarity (mol/L)} \times \text{Volume (L)} \times \text{Molar Mass (g/mol)}Mass (g)=Molarity (mol/L)×Volume (L)×Molar Mass (g/mol)
a) 1 L of 1 M solution of NaCl
Mass=1 mol/L×1 L×58.44 g/mol=58.44 g\text{Mass} = 1 \, \text{mol/L} \times 1 \, \text{L} \times 58.44 \, \text{g/mol} = 58.44 \, \text{g}Mass=1mol/L×1L×58.44g/mol=58.44g
Answer: 58.44 grams of NaCl are required.
b) 1 L of 0.5 M solution of NaCl
Mass=0.5 mol/L×1 L×58.44 g/mol=29.22 g\text{Mass} = 0.5 \, \text{mol/L} \times 1 \, \text{L} \times 58.44 \, \text{g/mol} = 29.22 \, \text{g}Mass=0.5mol/L×1L×58.44g/mol=29.22g
Answer: 29.22 grams of NaCl are required.
Explanation
The concept of molarity is fundamental in chemistry for preparing solutions. Molarity (M) is defined as the number of moles of solute (in this case, sodium chloride or NaCl) per liter of solution. The molar mass of NaCl is given as 58.44 grams per mole, meaning that one mole of NaCl weighs 58.44 grams. This value is calculated by summing the atomic masses of sodium (Na, approximately 22.99 g/mol) and chlorine (Cl, approximately 35.45 g/mol).
To prepare a 1 molar (1 M) solution, one needs exactly one mole of the solute dissolved in one liter of solution. Using the formula, we multiply the molarity by the volume in liters and the molar mass. For a 1 M solution, this means 1 mol of NaCl in 1 liter of solution, resulting in a requirement of 58.44 grams of NaCl.
For a 0.5 M solution, we need half the number of moles, since 0.5 moles of NaCl are required per liter. When this value is multiplied by the molar mass, it results in 29.22 grams of NaCl.
It is essential to weigh the exact mass using an analytical balance and then dissolve the salt in distilled or deionized water. After dissolving, the solution is typically transferred to a volumetric flask and diluted up to the 1-liter mark to ensure accuracy in concentration.
Precise solution preparation is crucial in chemical reactions, biological experiments, and industrial applications to ensure reliable and reproducible results.
