What mass of Ca(OH)2 is required to react with the acetic acid (CH3CO2H) in 25.0 mL of a solution having a density of 1.065 g/mL and containing 58.0% acetic acid by mass?

Answer: To calculate the mass of Ca(OH)2 required to react with acetic acid, we must follow a number of steps. These involve using the stoichiometry from the balanced chemical reaction between Ca(OH)2 and CH3CO2H, as well as using the given density and mass percent to determine the total amount of acetic acid in the solution.

The balanced chemical equation for the reaction between calcium hydroxide and acetic acid is: Ca(OH)2 + 2CH3CO2H → Ca(CH3CO2)2 + 2H2O

From this equation, we can see that one mole of Ca(OH)2 reacts with two moles of acetic acid (CH3CO2H).

Step 1: Calculate the mass of the acetic acid solution. mass of solution = volume × density mass of solution = 25.0 mL × 1.065 g/mL = 26.625 g (Note: 1 mL = 1 cm³ in volume)

Step 2: Calculate the mass of acetic acid in the solution. mass of acetic acid = mass of solution × percentage of acetic acid (as a decimal) mass of acetic acid = 26.625 g × 0.58 = 15.4425 g

Step 3: Convert the mass of acetic acid to moles. Moles of acetic acid = mass of acetic acid / molar mass of acetic acid The molar mass of CH3CO2H (acetic acid) is approximately 60.05 g/mol. moles of acetic acid = 15.4425 g / 60.05 g/mol ≈ 0.257 moles

Step 4: Determine moles of Ca(OH)2 needed. From the balanced equation, 1 mole of Ca(OH)2 reacts with 2 moles of CH3CO2H. moles of Ca(OH)2 = moles of acetic acid / 2 moles of Ca(OH)2 = 0.257 moles / 2 ≈ 0.1285 moles

Step 5: Calculate the mass of Ca(OH)2 required. Mass of Ca(OH)2 = moles of Ca(OH)2 × molar mass of Ca(OH)2 The molar mass of Ca(OH)2 is approximately 74.09 g/mol. mass of Ca(OH)2 = 0.1285 moles × 74.09 g/mol ≈ 9.52 g

So, approximately 9.52 grams of Ca(OH)2 is required to react completely with the acetic acid present in 25.0 mL of the given solution.

Extra: The concept being used here is stoichiometry, which is the calculation of reactants and products in chemical reactions. It's a core concept in chemistry that allows chemists to predict how much of each substance is needed or produced in a given reaction.

In this problem, we used the percent by mass of acetic acid in the solution to find the exact mass of acetic acid we're starting with. The density of the solution is also provided and is used to convert from volume to mass since we're given the volume of the acetic acid solution. Following this, we convert the mass of acetic acid to moles because chemical reactions occur in molar ratios.

Once we have the moles of acetic acid, we use the coefficients from the balanced chemical equation to find out how many moles of Ca(OH)2 are necessary. Since the reaction requires twice as many moles of acetic acid as calcium hydroxide, we divide the moles of acetic acid by two.

Lastly, by knowing the number of moles and the molar mass (the mass of one mole of a substance) of calcium hydroxide, we can find out the mass needed to react completely with the acetic acid present in the solution.