The concentration of urea in a solution prepared by dissolving 16 g of urea in 39 g of is __________% by mass. The molar mass of urea is 60.0 g/mol??

Answer 1

#29%#

You don't need to know the molar mass of urea to find the solution's percent concentration by mass, all you need is the mass of urea and the mass of water or the mass of the solution.

On that note, I presume that you're dissolving #"16 g"# of urea in #"39 g"# of water.
So, the idea here is that the solution's percent concentration by mass tells you the number of grams of urea, the solute, present for every #"100 g"# of the solution.
In your case, you get #"16 g"# of urea and #"39 g"# of water, so the total mass of the solution will be
#overbrace("16 g")^(color(blue)("mass of solute")) + overbrace("39 g")^(color(blue)("mass of solvent")) = overbrace("55 g")^(color(blue)("mass of solution"))#
So if you get #"16 g"# of urea in #"55 g"# of the solution, it follows that #"100 g"# of this solution will contain
#100 color(red)(cancel(color(black)("g solution"))) * "16 g urea"/(55color(red)(cancel(color(black)("g solution")))) = "29 g urea"#

This means that the solution's percent concentration by mass is equal to

#color(darkgreen)(ul(color(black)("% m/m = 29% urea")))#
This means that every #"100 g"# of this solution contain #"29 g"# of urea.

The answer is rounded to two sig figs.

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Answer 2

To find the concentration of urea in the solution, you first calculate the total mass of the solution (urea + water). Then, you divide the mass of urea by the total mass of the solution and multiply by 100 to get the percentage by mass.

Total mass of solution = mass of urea + mass of water

Total mass of solution = 16 g (urea) + 39 g (water) = 55 g

Percentage by mass of urea = (mass of urea / total mass of solution) * 100

Percentage by mass of urea = (16 g / 55 g) * 100 = 29.1%

So, the concentration of urea in the solution is 29.1% by mass.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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