10% (m/m) sodium hydroxide solution, NaOH, is used to break down wood fibre to make paper.
a) What mass of solute is needed to make 250mL of 10% (m/m) solution?
b) What mass of solvent is needed?
c) What is the molare concentration?
This question can't be answered exactly without knowing the density of q 10%(m/m) solution. That density based on the table at:
http://www.chembuddy.com/?left=CASC&right=density_tables
is 1.1111 g/ml. Use this density to find the mass of 250 mls.
(a) Calculate the mass of solute (10% of the mass of the solution).
(b) Find the mass of solvent (90% of the mass of the solution)
(c) Convert the mass of solute to moles by dividing it by the molar mass of NaOH.Then divide by 0.250 L to get the molar concentration.
To find the mass of solute needed to make 250mL of a 10% (m/m) sodium hydroxide solution, we can use the formula:
Mass of Solute = Volume of Solution (mL) × Percent Concentration (m/m)
For part (a), we have:
Volume of Solution = 250 mL
Percent Concentration = 10% (m/m)
Substituting the given values into the formula:
Mass of Solute = 250 mL × 10% (m/m)
To find the mass of the solute, we need to convert the percentage to a decimal by dividing it by 100:
Mass of Solute = 250 mL × (10/100)
Simplifying the equation:
Mass of Solute = 250 mL × 0.10
Mass of Solute = 25 grams
Therefore, the mass of the solute needed to make 250mL of a 10% (m/m) sodium hydroxide solution is 25 grams.
For part (b), we need to find the mass of the solvent. The solvent in this case is water, so to make a solution of 250mL, the mass of water needed is also 250 grams.
Therefore, the mass of the solvent needed is 250 grams.
For part (c), we need to find the molar concentration. The molar concentration of a solution is given by the formula:
Molar Concentration = Moles of Solute / Volume of Solution (in liters)
To find the molar concentration, we need to know the molar mass of sodium hydroxide. The molar mass of NaOH is 23 + 16 + 1 = 40 grams/mol.
We already found that the mass of the solute is 25 grams. To convert this to moles, we divide by the molar mass:
Moles of Solute = Mass of Solute / Molar Mass
Moles of Solute = 25 grams / 40 grams/mol
Moles of Solute = 0.625 mol
The volume of the solution is given as 250 mL, which is equivalent to 0.25 liters.
Now we can substitute the values into the molar concentration formula:
Molar Concentration = 0.625 mol / 0.25 L
Simplifying the equation:
Molar Concentration = 2.5 mol/L
Therefore, the molar concentration of the 10% (m/m) sodium hydroxide solution is 2.5 mol/L.
To answer these questions, we first need to understand what the terms "mass/mass" and "molar concentration" mean.
"Mass/mass" or "m/m" represents the concentration of a solution as the ratio of the mass of the solute to the mass of the entire solution. In this case, the concentration of the sodium hydroxide solution is 10% (m/m), meaning that for every 100 grams of the solution, 10 grams of sodium hydroxide are present.
Molar concentration, also known as molarity, is a measure of the concentration of a solute in a solution. It is given in moles per liter (mol/L) and represents the number of moles of solute present in one liter of the solution.
Now let's answer the questions step by step:
a) What mass of solute is needed to make 250 mL of 10% (m/m) solution?
To calculate the mass of solute needed, we will use the given percentage concentration and the volume of the solution.
First, convert the given volume of the solution to liters:
250 mL = 250/1000 = 0.25 L
Next, use the percentage 10% (m/m) to determine the mass of the solute. For a 10% m/m solution, 10 grams of solute are present in every 100 grams of the solution.
Therefore, for 0.25 L of solution, the mass of the solute can be calculated as follows:
Mass of solute = (10 g / 100 g) * 0.25 L = 0.025 g
So, 0.025 grams of sodium hydroxide is needed to make 250 mL of the 10% (m/m) solution.
b) What mass of solvent is needed?
The mass of the solvent can be determined by subtracting the mass of the solute from the total mass of the solution. Since the solution's volume is given, we can assume the density of the solution to be 1 g/mL.
The total mass of the solution can be calculated as follows:
Mass of solvent = Volume of solution - Mass of solute = 250 mL - 0.025 g = 249.975 g
Therefore, approximately 249.975 grams of solvent is needed.
c) What is the molar concentration?
To find the molar concentration of the solution, we need to convert grams of solute to moles and divide by the volume of the solution in liters.
The molar mass of sodium hydroxide (NaOH) is 23 g/mol for sodium (Na), 16 g/mol for oxygen (O), and 1 g/mol for hydrogen (H). So, the molar mass of NaOH is 23 + 16 + 1 = 40 g/mol.
Now, let's calculate the molar concentration:
Molar concentration (mol/L) = (Mass of solute (g) / Molar mass of solute (g/mol)) / Volume of solution (L)
= (0.025 g / 40 g/mol) / 0.25 L
= 0.01 mol/L
Therefore, the molar concentration of the solution is 0.01 mol/L.