Mole Fraction

Q.

QUESTION 2.5

A solution of glucose in water is labelled as $10\%w/w$. What should be the molality and mole fraction of each component in the solution? If the density of solution is $1.2gm{L}^{-1}$, then what shall be the molarity of the solution?

Q. The molarity of $900\text{g}$ of water is:

1. Cannot be calculated
2. $50\text{M}$
3. $55.5\text{M}$
4. $5\text{M}$

Q. A solution contains 25% water, 25% ethanol and 50% ethanoic acid by mass. Calculate the mole fraction of each component in the same order.

1. 0.301, 0.502, 0.196
2. 0.502, 0.196, 0.301
3. 0.245, 0.452, 0.502
4. 0.502, 0.196, 0.452

Q. The mole fraction of the solute in 2.5 molal aqueous solution is:

1. 0.051
2. 0.043
3. 0.156
4. 0.43

Q. What is the relation between molarity and mole fraction?

Q. At $300K$, the vapour pressure of a solution containing $1$ mole of $n-hexaneand3$ moles of $n-heptaneis550mmofHg$. At the same temperature, if one more mole of n-heptane is added to this solution, the vapour pressure of the solution increases by $10mmofHg$. What is the vapour pressure in $mmHg$ of n-heptane in its pure state ________?

Q.

Which of the following species by definition has ZERO standard Molar enthalpy of formation at 298 K?

1. ${\mathrm{Br}}_2\left(\mathrm{g}\right)$

2. ${\mathrm{CH}}_4\left(\mathrm{g}\right)$

3. ${\mathrm{Cl}}_2\left(\mathrm{g}\right)$

4. ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

Q. The relationship between molality (m) and mole fraction $\left({\chi }_A\right)$ of the solvent is:

1. $m=\frac{XA}{1-XA}\times \frac{1000}{X_A}$
2. $m=\frac{1-XA}{XA}\times \frac{1000}{M_A}$
3. $m=\frac{1-X_A}{XA}\times \frac{1000}{XB}$
4. $m=\frac{XA}{1-XA}\times \frac{1000}{XB}$

Q. A sugar syrup (containing sugar and water only) of weight 214.2 g contains 34.2 g of sugar ($C_{12}{H}_{22}{O}_{11}$). Find the mole fraction of the sugar in the syrup.

1. $0.1\times {10}^{-2}$
2. $9.9\times {10}^{-3}$
3. $9.9\times {10}^{-4}$
4. $0.1\times {10}^{-3}$

Q. The vapour density of a mixture containing $N{O}_2$ and $N_2{O}_4$ is $28.75$ at ${27}^o\text{C}$. Calculate the moles of $N{O}_2$ in $100\text{g}$ of the mixture.

1. $1.30$
2. $2.30$
3. $3.30$
4. $4.30$

Q. An aqueous solution is prepared by diluting 3.30 mL of acetone (density = 0.789 g/mL) to get the final volume of 75 mL. Find the mole fraction of acetone. (Assume no volume change on mixing).

1. 0.11
2. 0.1
3. 0.001
4. 0.01

Q.

QUESTION 2.38

Benzene and naphthalene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and naphthalene at 300 K are 50.71 mm Hg and 32.06 mm Hg respectively. Calculate the mole fraction of benzene in vapour phase if 80 g of benzene is mixed with 100 g of naphthalene.

Q.

How can I calculate the molality of pure water?

Q. In a $50mL$ solution of $H_2{O}_2$ an excess of $KI$ and dilute $H_{2}S{O}_4$ were added. The $I_2$ liberated required $20mL$ of $0.1NN{a}_2{S}_2{O}_3$ for complete reaction.
Calculate the strength of $H_2{O}_2$ in grams per litre.

1. $0.25g{L}^{-1}$
2. $0.34g{L}^{-1}$
3. $0.68g{L}^{-1}$
4. $0.8g{L}^{-1}$

Q. An ideal gas mixture of ethane $\left(C_2{H}_6\right)$ and ethene $\left(C_2{H}_4\right)$ occupies 28 litres at 1 atm and 273 K. The mixture reacts completely with 128 g of $O_2$ to produce $C{O}_2$ and $H_{2}O$. The mole fraction of $C_2{H}_6$ in the mixture is:

1. 0.6
2. 0.4
3. 0.5
4. 0.8

Q. The volume strength of $1\text{N}{H}_2{O}_2$ solution is:

1. $11.2\text{V}$
2. $22.4\text{V}$
3. $1\text{V}$
4. $5.6\text{V}$

Q. An ideal solution was obtained by mixing methanol and ethanol. If the partial vapour pressure of methanol and ethanole are 2.619 kPa and 4.556 kPa, respectively, the composition of vapour (in terms of mole fraction) will be

1. 0.635 MeOH, 0.365 EtOH
2. 0.365 MeOH, 0.635 EtOH
3. 0.574 MeOH, 0.326 EtOH
4. 0.173 MeOH, 0.827 EtOH

Q. $21g$ of $HN{O}_3$ is added to $250mL$ of water. Then choose the correct option:

1. $\text{Strength of the solution is}21g{L}^{-1}$
2. $\text{Molarity=2.33 M}$
3. $\text{Normality}=\text{Molarity}$
4. $\text{Normality}=2.66N$

Q. The mass percent of NaOH in water is 4.7%. What is the mole fraction of NaOH in the solution?

1. 0.022
2. 0.221
3. 0.177
4. 1.77

Q. What mass of ethanol $C_2{H}_{5}OH$ needs to be added to $1.0kg$ water so that the mole fraction of ethanol becomes $0.20?$

1. 93.5 g
2. 8.3 g
3. 638.89 g
4. 800 g

Q.

Define the following modes of expressing the concentration of a solution? Which of these modes are independent of temperature and why?
(a) w/w (mass percentage)

Define the following modes of expressing the concentration of a solution? Which of these modes are independent of temperature and why?
(b) V/V (volume percentage)

Define the following modes of expressing the concentration of a solution? Which of these modes are independent of temperature and why?
(c) w/V (mass by volume percentage)

Define the following modes of expressing the concentration of a solution? Which of these modes are independent of temperature and why?
(d) ppm (parts per million)

Define the following modes of expressing the concentration of a solution? Which of these modes are independent of temperature and why?
(e) x (mole fraction)

Define the following modes of expressing the concentration of a solution? Which of these modes are independent of temperature and why?
(f) M (molarity)

Define the following modes of expressing the concentration of a solution? Which of these modes are independent of temperature and why?
(g) m (molality)

Q. 49. If two substances A and B have Pa:Pb=1:2 and have mole fraction in solution as 1:2 then mole fraction of A in vapours is A)0.33 B)0.25 C)0.52 D)0.2

Q.

Define the following terms:

(i) Mole fraction

(ii) Molality

(iii) Molarity

(iv) Mass percentage.

Q. How many grams of oxygen $\left(O_2\right)$ are required to completely react with $0.20\text{g}$ of hydrogen $\left(H_2\right)$ to yield water $\left(H_{2}O\right)$? (molar mass $H_2=2\text{g/mol},O_2=32\text{g/mol}$)

Q. At STP the density of $CC{l}_4$ vapour in $\text{g/L}$ will be nearest to:

1. $6.87$
2. $3.42$
3. $10.26$
4. $4.57$

Q.

A hydrocarbon $X$ contains $85.7\%$ carbon by mass. If the relative molecular mass of $X$ is $28$ , find the molecular formula of $X$.

Q. 45. water is added to the solution M such that the mole fraction of water in the solution becomes 0.9 the booling point of this solution is a) 380.4 k b) 376.2 k c) 375.5 k d) 354.7 k

Q. What would be the molality of $20\%$ (mass/mass) aqueous solution of $KI$ ?
Molar mass of $KI$ is $166gmo{l}^{-1}$

1. $1.51$
2. $1.35$
3. $1.08$
4. $1.48$

Q. The $O{H}^{-}$ concentration in a mixture of 5.0mL of 0.0504 M$N{H}_{4}Cl$ and 2 mL of $0.0210MN{H}_3$ solution is $x\times {10}^{-6}M$. The value of x is .......(Nearest integer) [Given $K_W=1\times {10}^{-14}andKb=1.8\times {10}^{-5}$]

Q. When a coordination compound $NiC{l}_2.6H_{2}O$ is mixed with $AgN{O}_3,2$ moles of AgCl are precipitated per mole of the compound. Write:

(i) Structural formula of the complex
(ii) IUPAC name of the complex.