A solution with a final volume of 750.0 mL was prepared by dissolving 30.00 mL of benzene (C 6 H 6 , density = 0.8787 g/mL) in dichloromethane. Calculate the molarity of benzene in the solution.

In this practice question it says, a solution with a final volume of 750 milliliters was prepared by dissolving 30 milliliters of benzene. Benzene has a molecular formula of c 6 H6 and a density of 0.8787 grams per milliliter, and it was done so in dichloromethane. We're gonna say calculate the molarity of benzene in the solution. So here they want us to calculate molarity. Since it's molarity of benzene, it would be moles of benzene over liters of solution. From what they tell us in the question, we know that the final volume of the solution is 750 ml's. We're gonna convert those ml's into liters. Now and remember, 1 milliliter is 10 to the negative 3 liters. So that would be 0.7 50 liters. That can go here on the bottom. Next, we have the volume of benzene, we have the density of benzene. We can use those to calculate the mass of benzene. So we have 30 milliliters of benzene, and it is 1 milliliter of benzene for every 0.8787 grams of benzene. Now that we have grams of benzene, we just have to convert those grams into moles. So grams of benzene go on the bottom so they can cancel out. One mole of benzene goes on top. We add up the 6 carbons and the 6 hydrogens from the periodic table, and if you do that correctly, you should get a total mass of 78.108 grams. So here grams cancel out and now we're gonna have moles of benzene, which comes out to 0.33749 moles of benzene. So take those moles and plug them in. When we do that, we get 0.449987 molar. We look at the number of sig figs within our question. So 750.0 has 4 sig figs, 30.00 has 4 sig figs, and 0.8787 also has 4 sig figs. So we have to have 4 sig figs at the end. So that's 0.4500 molar for our benzene solution. So just remember, they're asking us for molarity, use the molarity formula to help organize your information, and then solve for the missing variables. Doing that helps us to find molarity in this particular case.

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9. Solutions

Molarity

GOB Chemistry

9. Solutions

Molarity

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Multiple Choice

A solution with a final volume of 750.0 mL was prepared by dissolving 30.00 mL of benzene (C₆H₆, density = 0.8787 g/mL) in dichloromethane. Calculate the molarity of benzene in the solution.

0.45 M

0.035 M

0.35 M

0.71 M

0.091 M

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Verified step by step guidance

First, calculate the mass of benzene using its volume and density. Use the formula: \( \text{mass} = \text{volume} \times \text{density} \). Here, the volume of benzene is 30.00 mL and the density is 0.8787 g/mL.

Next, convert the mass of benzene to moles. Use the molar mass of benzene (C6H6), which is approximately 78.11 g/mol. The formula to use is: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \).

Now, calculate the molarity of benzene in the solution. Molarity (M) is defined as the number of moles of solute per liter of solution. Use the formula: \( M = \frac{\text{moles of benzene}}{\text{volume of solution in liters}} \).

Convert the final volume of the solution from milliliters to liters. Since the final volume is 750.0 mL, divide by 1000 to convert to liters.

Finally, substitute the values obtained for moles of benzene and volume of solution in liters into the molarity formula to find the molarity of benzene in the solution.