Question

What is the molarity of a bleach solution containing 9.5 \(\mathrm{g}\) of \(\mathrm{NaOCl}\) per liter of bleach?

Short answer

The molarity of the bleach solution containing 9.5 g of NaOCl per liter is approximately 0.1276 M. This is calculated by first finding the molar mass of NaOCl (74.44 g/mol), then calculating the moles of NaOCl in the solution (0.1276 mol), and finally dividing the moles of NaOCl by the volume of the solution in liters (1 L) to find the molarity.

Step-by-step solution

Find the molar mass of NaOCl

To find the moles of NaOCl in the solution, we first need to know the molar mass of NaOCl. The molar mass is the sum of the atomic masses of the elements in the formula. In this case, NaOCl consists of sodium (Na), oxygen (O), and chlorine (Cl). Using their atomic masses, we calculate the molar mass of NaOCl as follows: Molar mass of NaOCl = (22.99 g/mol for Na) + (16.00 g/mol for O) + (35.45 g/mol for Cl) = 74.44 g/mol

Calculate the moles of NaOCl in the solution

Now that we have the molar mass of NaOCl, we can calculate the moles of NaOCl in the bleach solution. We were given that there are 9.5 g of NaOCl per liter of bleach. So, using the molar mass, we can find the moles of NaOCl as follows: moles of NaOCl = mass of NaOCl (g) / molar mass of NaOCl (g/mol) = 9.5 g / 74.44 g/mol = 0.1276 mol

Determine the molarity (M) of the bleach solution

Now that we have the moles of NaOCl, we can find the molarity of the solution. We were given that the bleach solution has a volume of 1 liter. So, the molarity is: Molarity (M) of NaOCl = moles of NaOCl / volume of solution in liters = 0.1276 mol / 1 L = 0.1276 mol/L The molarity of the bleach solution containing 9.5 g of NaOCl per liter is approximately 0.1276 M.

Key concepts

Molar Mass

Molar mass is a key concept in chemistry, representing the mass of one mole of a given substance. Essentially, it's the formula weight expressed in grams per mole. Molar mass helps in converting between the mass of a substance and the number of moles, which is essential for stoichiometric calculations such as calculating solutions' concentrations. The molar mass is determined by summing the atomic masses of all the atoms in a molecule.
For example, in the compound sodium hypochlorite (NaOCl):

• Sodium (Na) has an atomic mass of 22.99 g/mol.
• Oxygen (O) has an atomic mass of 16.00 g/mol.
• Chlorine (Cl) has an atomic mass of 35.45 g/mol.

When you add these together: 22.99 + 16.00 + 35.45, you get 74.44 g/mol, which is the molar mass of NaOCl.
This measurement is crucial for accurately determining how many molecules are present in a sample of a substance based on its weight.

Sodium Hypochlorite

Sodium hypochlorite is a chemical compound with the formula NaOCl. It's widely recognized as a bleaching agent and disinfectant found in household bleach. Sodium hypochlorite is effective in sanitizing surfaces and whitening clothing, thanks to its oxidative properties.
Sodium hypochlorite is commonly produced by passing chlorine gas through a sodium hydroxide solution, a process that results in the formation of NaOCl. When used in solutions, NaOCl releases hypochlorous acid (HOCl), which is its active component in disinfection. This acid effectively kills bacteria, viruses, and fungi, making sodium hypochlorite a versatile and powerful cleaning substance.
Its usability in disinfectants is due largely to the direct oxidative action on cellular components of microorganisms. Therefore, its effectiveness and commonality in cleaning products make sodium hypochlorite a household staple.

Chemical Solution Concentration

Chemical solution concentration is a measure of how much solute is dissolved in a specified volume of solution. In chemistry, concentration can be expressed in various ways, but molarity is the most common unit. Molarity (M) is defined as the number of moles of solute per liter of solution.
To calculate molarity, you use the formula:

• \( \text{Molarity (M)} = \frac{\text{moles of solute}}{\text{liters of solution}} \)

For example, if you dissolve 9.5 g of NaOCl in 1 liter of water and you know the molar mass of NaOCl (74.44 g/mol), you find the number of moles by dividing the grams by the molar mass \((9.5 \text{ g} / 74.44 \text{ g/mol} = 0.1276 \text{ mol})\).
Then, calculate the molarity by inserting it into the formula: 0.1276 moles per 1 L equals 0.1276 M.
Understanding concentration helps in preparing solutions with precise chemical characteristics, important in both laboratory settings and everyday applications such as cooking, cleaning, and medicinal dosing.