Answer
Verified
388.2k+ views
Hint:We will take the help of the formula of Mass percentage. It is the amount of solute present in $100g$ of solution. By this we can find the number of moles i.e. the number of moles is the ratio of given weight of solute to the molar mass of the solute.
Formula used: Mass percentage$ = \dfrac{{Mass{\text{ of solute}}}}{{Mass{\text{ of solution}}}} \times 100$
Complete answer:
Given: Volume of water $ = 250ml$
Density of water$ = 0.999g/ml$
Since density $ = \dfrac{{Mass{\text{ of water}}}}{{Volume{\text{ of water}}}}$
$
6.999 = \dfrac{{Mass{\text{ of water}}}}{{250}} \\
\therefore Mass{\text{ of water}} = 0.999 \times 250 \\
$
$ = 249.75gm$
Since ammonia dissolved in ${H_2}O$ is \[30\% \]by weight
By using the formula, mass percentage$ = \dfrac{{Mass{\text{ of solute}}}}{{Mass{\text{ of solution}}}} \times 100$
Mass percentage $ = \dfrac{{Mass{\text{ of solute}}}}{{Mass{\text{ of solute}} + mass{\text{ of solvent}}}} \times 100$
$\therefore $$Mass{\text{ percentage}}$$ = \dfrac{{Mass{\text{ of ammonia}}}}{{Mass{\text{ of ammonia}} + mass{\text{ of water}}}} \times 100$
Now, let the mass of ammonia be mass percentage is $30\% $ and mass of water is $249.75gm,$by putting the values we will get-
$\dfrac{{30}}{{100}} = \dfrac{x}{{x + 249.75}}$
$
30x + 7492.5 = 100x \\
70x = 7492.5{\text{ }} \\
\therefore {\text{x = 107}}{\text{.03gm}}{\text{.}} \\
$
Thus mass of ammonia dissolved in \[250ml\] of water is \[107.03gm\]
To find the number of moles of ammonia we will use this formula
Number moles of $N{H_3} = \dfrac{{Mass{\text{ of ammonia}}}}{{Molar{\text{ mass}}}}$
\[
= \dfrac{{107.03g}}{{17g/mol}} \\
= 6.3moles \\
\]
Hence the correct answer is option B.
Note: it is very important to know how the amount of substance is expressed when it is present in the form of a solution. The concentration of a solution or the amount of substance present in its given volume can be expressed in any of the following ways: mass percentage, mole fraction, molality and normality. Mass percentage is independent of temperature.
Formula used: Mass percentage$ = \dfrac{{Mass{\text{ of solute}}}}{{Mass{\text{ of solution}}}} \times 100$
Complete answer:
Given: Volume of water $ = 250ml$
Density of water$ = 0.999g/ml$
Since density $ = \dfrac{{Mass{\text{ of water}}}}{{Volume{\text{ of water}}}}$
$
6.999 = \dfrac{{Mass{\text{ of water}}}}{{250}} \\
\therefore Mass{\text{ of water}} = 0.999 \times 250 \\
$
$ = 249.75gm$
Since ammonia dissolved in ${H_2}O$ is \[30\% \]by weight
By using the formula, mass percentage$ = \dfrac{{Mass{\text{ of solute}}}}{{Mass{\text{ of solution}}}} \times 100$
Mass percentage $ = \dfrac{{Mass{\text{ of solute}}}}{{Mass{\text{ of solute}} + mass{\text{ of solvent}}}} \times 100$
$\therefore $$Mass{\text{ percentage}}$$ = \dfrac{{Mass{\text{ of ammonia}}}}{{Mass{\text{ of ammonia}} + mass{\text{ of water}}}} \times 100$
Now, let the mass of ammonia be mass percentage is $30\% $ and mass of water is $249.75gm,$by putting the values we will get-
$\dfrac{{30}}{{100}} = \dfrac{x}{{x + 249.75}}$
$
30x + 7492.5 = 100x \\
70x = 7492.5{\text{ }} \\
\therefore {\text{x = 107}}{\text{.03gm}}{\text{.}} \\
$
Thus mass of ammonia dissolved in \[250ml\] of water is \[107.03gm\]
To find the number of moles of ammonia we will use this formula
Number moles of $N{H_3} = \dfrac{{Mass{\text{ of ammonia}}}}{{Molar{\text{ mass}}}}$
\[
= \dfrac{{107.03g}}{{17g/mol}} \\
= 6.3moles \\
\]
Hence the correct answer is option B.
Note: it is very important to know how the amount of substance is expressed when it is present in the form of a solution. The concentration of a solution or the amount of substance present in its given volume can be expressed in any of the following ways: mass percentage, mole fraction, molality and normality. Mass percentage is independent of temperature.
Recently Updated Pages
Basicity of sulphurous acid and sulphuric acid are
Three beakers labelled as A B and C each containing 25 mL of water were taken A small amount of NaOH anhydrous CuSO4 and NaCl were added to the beakers A B and C respectively It was observed that there was an increase in the temperature of the solutions contained in beakers A and B whereas in case of beaker C the temperature of the solution falls Which one of the following statements isarecorrect i In beakers A and B exothermic process has occurred ii In beakers A and B endothermic process has occurred iii In beaker C exothermic process has occurred iv In beaker C endothermic process has occurred
What is the stopping potential when the metal with class 12 physics JEE_Main
The momentum of a photon is 2 times 10 16gm cmsec Its class 12 physics JEE_Main
How do you arrange NH4 + BF3 H2O C2H2 in increasing class 11 chemistry CBSE
Is H mCT and q mCT the same thing If so which is more class 11 chemistry CBSE
Trending doubts
Difference Between Plant Cell and Animal Cell
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
How do you solve x2 11x + 28 0 using the quadratic class 10 maths CBSE
Select the correct plural noun from the given singular class 10 english CBSE
What organs are located on the left side of your body class 11 biology CBSE
The sum of three consecutive multiples of 11 is 363 class 7 maths CBSE
What is the z value for a 90 95 and 99 percent confidence class 11 maths CBSE
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
How many squares are there in a chess board A 1296 class 11 maths CBSE