Some basic concepts of chemistry practice · Hard

One mole of mixture of $\mathrm{N}_2, \mathrm{NO}_2$ and $\mathrm{N}_2 \mathrm{O}_4$ has a mean molar mass of $55.4 \mathrm{~g}.$ On heating to a temperature, at which all the $\mathrm{N}_2 \mathrm{O}_4$ is dissociated into $\mathrm{NO}_2,$ the mean molar mass tends to a lower value of $39.6 \mathrm{~g}.$ What is the mole ratio of $\mathrm{N}_2, \mathrm{NO}_2$ and $\mathrm{N}_2 \mathrm{O}_4$ in the original mixture?

What will be the minimum molar mass of a compound containing $0.39 \%$ of nickel?

The number of moles of $KMn{O_4}$ that will be needed to react completely with one mole of oxalate ion in acidic solution is

An unknown compound $\mathrm{A}$ dissociates at $500^{\circ} \mathrm{C}$ to give products as follows $A(g) \rightleftarrows B(g)+C(g)+D(g)$ Vapour density of the equilibrium mixture is 50 when it dissociates to the extent to $10 \%$. What will be the molecular weight of compound A-

A mixture of $\mathrm{NaHC}_2 \mathrm{O}_4$ and $\mathrm{KHC}_2 \mathrm{O}_4 \cdot \mathrm{H}_2 \mathrm{C}_2 \mathrm{O}_4$ required equal volumes of $0.2 \mathrm{~N} \mathrm{~KMnO}_4$ and $0.12 \mathrm{~N} \mathrm{NaOH}$ separately. What is the molar ratio of $\mathrm{NaHC}_2 \mathrm{O}_4$ and $\mathrm{KHC}_2 \mathrm{O}_4 \cdot \mathrm{H}_2 \mathrm{C}_2 \mathrm{O}_4$ in the mixture?

The sulphate of an element contains $42.2 \%$ element. The equivalent weight of the metal would be

Two elements $X$ and $Y$ have atomic weights of 14 and 16. They form a serics of compounds $A, B, C, D$ and $E$ in which the same amount of element ${X},{Y}$ is present in the ratio $1: 2: 3: 4: 5.$ If the compound $A$ has 28 parts by weight of $X$ and 16 parts by weight of ${Y},$ then the compound of ${C}$ will have 28 parts weight of ${X}$ and

$0.40 \mathrm{~g}$ of helium in a bulb at a temperature of $T \mathrm{~K}$ had a pressure of $p$ atm. When the bulb was immersed in water bath at temperature $50 \mathrm{~K}$ more than the first one, $0.08 \mathrm{~g}$ of gas had to be removed to restore the original pressure. $T$ is

Calculate the molality of 1 litre solution of $93 \% \, \mathrm{H}_2 \mathrm{SO}_4$ (weight/volume). The density of the solution is $1.84 \mathrm{~g} / \mathrm{mL}$.

Iron forms two oxides. If for the same mass of iron, the mass of oxygen combined in the first oxide is two-third of the mass of oxygen combined in the second oxide, then the ratio of valency of iron in first and second oxide is

At 300 K and 1 atm, 15 mL of a gaseous hydrocarbon requires 375 mL air containing 20% ${O_2}$ by volume for complete combustion. After combustion, the gases occupy 330 mL. Assuming that the water formed is in liquid form and the volumes were measured at the same temperature and pressure, the formula of the hydrocarbon is

For the reaction,

$\mathrm{FeS}_2+\mathrm{KMnO}_4+\mathrm{H}^* \longrightarrow \mathrm{Fe}^{3+}+\mathrm{H}_2 \mathrm{SO}_4+\mathrm{Mn}^{2+}+\mathrm{H}_2 \mathrm{O}$

if the molar mass of $\mathrm{FeS}_2$ is $\mathrm{M}$, then equivalent mass of $\mathrm{FeS}_2$ would be equal to

Rearrange the following (I to IV) in the order of increasing masses and choose the correct answer from (1), (2), (3) and (4) (Atomic mass: $N=14, O=16, C u=63$).

I. 1 molecule of oxygen

II. 1 atom of nitrogen

III. $1 \times 10^{-10} \mathrm{~g}$ molecular weight of oxygen

IV. $1 \times 10^{-10} \mathrm{~g}$ atomic weight of copper

How many litres of detonating gas may be produced at $0^{\circ} \mathrm{C}$ and $1 \mathrm{~atm}$ from the decomposition of 0.1 mole of water by an electric current?

$25 \mathrm{~ml}$ solution containing $\left(6.35 \mathrm{~g} / \mathrm{L}\right.$ of $\mathrm{K} \mathrm{H}_3\left(\mathrm{C}_2 \mathrm{O}_4\right)_2 \cdot 2 \mathrm{H}_2 \mathrm{O}$ required $\mathrm{V}_1 \mathrm{ml}$ of $0.1 \mathrm{~N}$ $\mathrm{NaOH}$ and $\mathrm{V}_2 \mathrm{ml}$ of $0.1 \mathrm{~N} \mathrm{~KMnO}_4$ in two separate titrations. Calculate $\mathrm{V}_1$ and $\mathrm{V}_2$.
$\mathrm{KH}_3\left(\mathrm{C}_2 \mathrm{O}_4\right)_2 \cdot 2 \mathrm{H}_2 \mathrm{O} ; \mathrm{M}_0=254 \mathrm{~gm} / \mathrm{mol}$

One $\mathrm{g}$ of impure $\mathrm{Na}_2 \mathrm{CO}_3$ is dissolved in water and the solution is made upto $250 \mathrm{~mL}$. To $50 \mathrm{~mL}$ of this made up solution, $50 \mathrm{~mL}$ of $0.1 \mathrm{~N} \mathrm{~HCl}$ is added and the mixture after shaking well required $10 \mathrm{~mL}$ of $0.16 \mathrm{~N}$ sodium hydroxide solution for complete neutralization. Calculate the per cent purity of the sample of $\mathrm{Na}_2 \mathrm{CO}_3$.

A 0.518 g sample of lime stone is dissolved in $HCl$ and then the calcium is precipitated as $\mathrm{Ca}{\mathrm{C}_2}{\mathrm{O}_4}$. After filtering and washing the precipitate, it requires 40.0 mL of $0.250N\mathrm{KMn}{\mathrm{O}_4},$, solution acidified with ${\mathrm{H}_2}\mathrm{S}{\mathrm{O}_4}$ to titrate is as, $\mathrm{MnO}_4^ - + {\mathrm{H}^ + } + {\mathrm{C}_2}\mathrm{O}_4^{2 - } \to \mathrm{M}{\mathrm{n}^{2 + }} + \mathrm{C}{\mathrm{O}_2} + 2{\mathrm{H}_2}\mathrm{O}$. The percentage of $\mathrm{CaO}$ in the sample is :

Calculate the molality of 1 litre solution of $93 \% \, \mathrm{H}_2 \mathrm{SO}_4$ (weight/volume). The density of the solution is $1.84 \mathrm{~g} / \mathrm{mL}$.

1 mol each of ${H}_3 {PO}_2, {H}_3 {PO}_3$ and ${H}_3 {PO}_4$ will neutralize $x \mathrm{~mol}$ of ${NaOH}, y \mathrm{~mol}$ of ${Ca}({OH})_2$ and ${z} \mathrm{~mol}$ of ${Al}({OH})_3 . x, y$ and $z$ are in the ratio

The density of $3 \mathrm{M}$ solution of sodium chloride is $1.252 \mathrm{~g} \mathrm{~mL}^{-1}$. The molality of the solution will be:

(molar mass, $\mathrm{NaCl}=58.5 \mathrm{~g} \mathrm{~mol}^{-1}$ )

In the given chemical reaction, colours of the $\mathrm{F}{\mathrm{e}^{\mathrm{2 + }}}\,\,\mathrm{and}\,\,\mathrm{ F}{\mathrm{e}^{\mathrm{3 + }}}$ ions, are respectively
$\mathrm{5}F{e^{\mathrm{2 + }}}\mathrm{ + }M\mathrm{n}O_4^ - + 8{H^ + } \to M{n^{2 + }} + 4{H_2}O + 5F{e^{3 + }}$

Chlorofluorocarbons such as ${CCl}_3 {F}(\mathrm{M}=137.5)$ and ${CCl}_2 {F}_2(\mathrm{M}=121)$ have been linked to ozone depletion in Antarctica. As of 2004, these gases were found in 275 and 605 parts per trillion $\left(10^{12}\right),$ by volume. What are the concentrations of these gases under conditions typical of Antarctica stratosphere $(200 \mathrm{~K}$ and $0.08 \mathrm{~atm}) ?(R=0.08 \, l \text{-atm/K-mol})$

The number of gram atoms of oxygen present in 0.3 gram mole of $({COOH})_2 \cdot 2 {H}_2 {O}$ is

The mineral haematite is $\mathrm{Fe}_2 \mathrm{O}_3$. Haematite ore contains unwanted material called gangue in addition of $\mathrm{Fe}_2 \mathrm{O}_3$. If $5.0 \mathrm{~kg}$ of ore contains $2.78 \mathrm{~kg}$ of $\mathrm{Fe}$, what per cent of ore is $\mathrm{Fe}_2 \mathrm{O}_3$?

If the weight of metal oxide is ${xg}$ containing ${yg}$ of oxygen, the equivalent weight of metal will be

If $m_A$ gram of a metal $A$ displaces $m_B$ gram of another metal $B$ from its salt solution and if the equivalent weights are $E_A$ and $E_B$ respectively then equivalent weight of $A$ can be expressed as:

$40 \mathrm{ml}$ of $0.8 \mathrm{~N}$ oxalic acid dihydrate is shaken with $0.75 \mathrm{~g}$ active charcoal. The final concentration of the solution after adsorption is $0.2 \mathrm{~N}$. What is the amount of oxalic acid adsorbed per gm of carbon?

What is the mass of $3.01 \times 10^{22}$ molecules of ammonia?

Cupric ammonium sulphate was found to contain
$27.03\%$ water of crystallization by mass. Upon
strongly heating, it gave cupric oxide corresponding
to $19.89\%$ of starting mass. Find the empirical
formula of cupric ammonium sulphate. $(\text{Cu} = 63.5)$

Mole fraction of solute in an aqueous solution of $\mathrm{NaOH}$ is $0.1.$ If the specific gravity of the solution is $1.4,$ then the molarity of the solution is