30.0 g of NaCl(s) is added to water to make 800 mL of salt solution.
a. Determine the number of moles in 30.0 g of NaCl(s).
b. Calculate the molar concentration of this salt solution.
moles = g/molar mass = 30.0/58.5 = ?
M = moles/L of solution = moles/0.800 = ?
a. To determine the number of moles in 30.0 g of NaCl(s), we need to use the formula:
Number of moles = Mass / Molar mass
The molar mass of NaCl is the sum of the atomic masses of sodium (Na) and chlorine (Cl), which is 22.99 g/mol + 35.45 g/mol = 58.44 g/mol.
Number of moles = 30.0 g / 58.44 g/mol
b. Now, to calculate the molar concentration of the salt solution, we need to use the formula:
Molar concentration (M) = Number of moles / Volume (in liters)
Given that the volume is 800 mL, we need to convert it to liters by dividing by 1000.
Volume = 800 mL / 1000 mL/L = 0.8 L
Molar concentration (M) = Number of moles / Volume
Substituting the number of moles we calculated in part a:
Molar concentration (M) = (30.0 g / 58.44 g/mol) / 0.8 L
To determine the number of moles in 30.0 g of NaCl(s), we need to use the molar mass of NaCl and the formula:
a. Number of moles = Mass of substance / Molar mass
1. The molar mass of NaCl is 58.44 g/mol. This is the sum of the atomic masses of sodium (Na) and chlorine (Cl). The atomic masses are found on the periodic table.
2. Substitute the given values into the formula:
Number of moles = 30.0 g / 58.44 g/mol
3. Calculate the result:
Number of moles = 0.514 mol (rounded to three decimal places)
Therefore, there are approximately 0.514 moles of NaCl in 30.0 g of NaCl(s).
Now, let's move on to calculating the molar concentration of the salt solution.
b. Molar concentration (also known as molarity) is defined as the number of moles of solute (in this case, NaCl) divided by the volume of the solution in liters.
1. The volume of the solution is given as 800 mL, but it needs to be converted to liters for consistent units. There are 1000 mL in 1 L, so:
Volume of solution = 800 mL / 1000 mL/L
Volume of solution = 0.800 L
2. Now, substitute the values into the formula:
Molar concentration = Number of moles / Volume of solution
Molar concentration = 0.514 mol / 0.800 L
3. Calculate the result:
Molar concentration = 0.6425 mol/L (rounded to four decimal places)
Therefore, the molar concentration of this salt solution is approximately 0.6425 mol/L.