What is the mass percent of NH 3 of a 1.25 m aqueous solution of NH 3 ?

What is the mass percent of NH3 of a 1.25 molar aqueous solution of NH3? Alright, so we want mass percent of NH 3. So that would mean that we want grams of NH 3 divided by grams of solution times 100. All they give me here is the molality, so we have 1.25 moles of NH 3. What does that really mean? Expand it out. That means we have 1.25 moles of NH 3, divided by 1 kilogram of our solvent, which would be water because it's an aqueous solution. Alright, so we have moles of NH 3, we have kilograms of water, we can change both of those to grams and plug them into my math percent equation. So, we have 1.25 moles of NH 3, We have 1 nitrogen, 3 hydrogens. When you add up all the masses from the periodic table, it's 17.034 grams for every 1 mole. Moles cancel out and we have 21.29 25 grams of NH 3. Our 1 kilogram of water is equal to 1,000 grams of water. Now, we can plug these numbers into our formula. So, we have 21.2925 grams of NH 3. Remember, grams of solution is the grams of your solute, which is the NH 3, plus the grams of our solvent, which is the water. So, we're adding those two numbers together here on the bottom. And then all of this is going to get multiplied by a 100 to give us our percentage. So, that comes out to being 2 point 0 8 percent as the mass percent of NH 3. So again, repeated patterns. We're doing dimensional analysis with molality and mass percent, Write down what they're asking us to find, list the given information, isolate the units that you need to get your final answer at the end.

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9. Solutions

Molality

GOB Chemistry

9. Solutions

Molality

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Multiple Choice

What is the mass percent of NH₃ of a 1.25 m aqueous solution of NH₃?

1.11%

3.53%

2.08%

87.4%

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Verified step by step guidance

Understand that mass percent is calculated as the mass of the solute divided by the total mass of the solution, multiplied by 100.

Recognize that a 1.25 m (molal) solution means there are 1.25 moles of NH3 per kilogram of water.

Calculate the mass of NH3 using its molar mass. The molar mass of NH3 is approximately 17.03 g/mol. Multiply 1.25 moles by 17.03 g/mol to find the mass of NH3 in grams.

Since the solution is 1.25 m, it contains 1 kg (1000 g) of water. Add the mass of NH3 to the mass of water to find the total mass of the solution.

Calculate the mass percent of NH3 by dividing the mass of NH3 by the total mass of the solution and then multiplying by 100 to convert it to a percentage.