Question

the concentration (w/w%) of a 200g solution of common salt is 10% if 20g more water is mixed in it then its concentration becomes
1. 10.10%
2.11.11%
3.9.99%
4.9.09%

please answer fast​

Answer 1

Given,

The concentration (w/w%) of common salt = 10%

Mass of the solution = 200 grams

To find,

The concentration if 20 grams of water is added to the solution.

Solution,

Let,the mass of the solute or the common salt = x grams

[Assume, x as a variable to do the further mathematical calculations.]

Now,we have to apply the w/w% concentration formula,

Concentration (w/w%) = 100 × Mass of solute/Mass of solution

10 = 100 × x/200

x/2 = 10

x = 20

Mass of solute = 20

Now, mass of the solution after water addition = 200+20 = 220 grams

So,final concentration (w/w%) = 100 × 20/220 = 9.09%

Hence, the final concentration (w/w%) will be 9.09% or Option 3.

Answer 2

If 20g more water is mixed in it then the concentration of solution becomes 9.09%

Therefore, option (4) is correct.

Explanation:

Let the weight of sugar in the initial concentration was x

We know that

concentration of a solution (w/w) % = (Weight of solute/Weight of solution) × 100

Given that the initial concentration is 10% and the weight of solution is 200 g

Therefore,

$10=\frac{x}{200}\times 100$

$\implies x=20$ gram

If 20 g more water is added

Then the weight of solution = 200 + 20 = 220 gram

The new concentration

$=\frac{20}{220}\times 100$

$=9.09\%$

Hope this answer is helpful.

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