Empirical & Molecular Formula

Q.

The equivalent weight of crystalline Oxalic acid is

Q. STATEMENT-1: Two compounds cannot have the same empirical formula.

STATEMENT-2: Compounds that have the same empirical formula may have different molecular formulae.

1. Both the statements are true.
2. Both the statements are false.
3. Statement-1 is true, but statement-2 is false.
4. Statement-1 is false, but statement-2 is true.

Q. The number of moles of carbon dioxide which contain 8 g of oxygen is

1. 0.40 mol
2. 0.5 mol
3. 0.20 mol
4. 0.25 mol

Q. An organic compound contains C, H and S the minimum molecular weight of the compound containing 10% sulphur is : (atomic weight of S=32 amu)

1. $400gmo{l}^{-1}$
2. $320gmo{l}^{-1}$
3. $520gmo{l}^{-1}$
4. $600gmo{l}^{-1}$

Q.

Write the chemical formula for the covalent compound hydrogen iodide and mention its molecular weight in brackets after the formula.

Q. An acid is a component of rancid butter and has a vile stench. Burning 0.44 g of the acid in excess oxygen yield 0.88 g of $C{O}_2$ and 0.36 g of $H_{2}O$ as the only products. Given that the acid contains only C, H, and O and if vapour density of the acid is 44, then which of the following options is not correct about it’s molecular formula?

1. It contains 4 carbon atoms
2. It contains 6 hydrogen atoms
3. It contains 2 oxygen atoms
4. Its empirical formula contains 2 carbon atoms

Q. The empirical formula of a gaseous fluorocarbon is $C{F}_2$. At a certian temperature and pressure, a 1 L volume hold 8.95 g of this fluorocarbon. Under the same conditions, 1 L volume holds only 1.70 g gaseous $F_2$. Thus, fluorocarbon is_______.
(F = 19)

1. $C{F}_2$
2. $C_2{F}_4$
3. $C_3{F}_6$
4. $C_4{F}_8$

Q. A mineral consists of an equimolar mixture of the carbonates of two bivalent metals. One metal is present to the extent of $20\%$ by weight. $3.0g$ of the mineral on heating lost $1.1g$ of $C{O}_2$. What is the $\%$ by weight of the other metal?

1. $70\%$
2. $33\%$
3. $67\%$
4. $30\%$

Q. $11.6g$ of an organic compound having formula $C_n{H}_{2n+2}$ is burnt in excess of $O_2\left(g\right)$ initially taken in a $22.41$ litre steel vessel. Before reaction, the gaseous mixture was at $273K$ with pressure reading $2atm$. After complete combustion and loss of considerable amount of heat, the mixture of product and excess of $O_2$ had a temperature of $546K$ and $4.6atm$ pressure. The formula of organic compound is:

1. $C_2{H}_6$
2. $C_3{H}_8$
3. $C_5{H}_{12}$
4. $C_4{H}_{10}$

Q. An organic compound contains carbon and hydrogen. Its elemental analysis gave $C-75\%$ and $H-25\%$. The empirical formula of the compound would be:

1. $C{H}_4$
2. $C{H}_3$
3. $C{H}_2$
4. $CH$

Q. The sulphate of a metal M contains $9.87\%$ of $M$. This sulphate is isomorphous with $ZnS{O}_4.7H_{2}O$. The metal can be:

1. Calcium
2. Iron
3. Manganese
4. Magnesium

Q. The empirical formula of a compound is $C{H}_{2}O$. If 0.0833 moles of the compound contains 1 g of hydrogen, find the molecular formula of the compound.

1. $C_5{H}_{10}{O}_5$
   
2. $C_6{H}_{12}{O}_6$
   
3. $C_4{H}_8{O}_4$
   
4. $C_3{H}_6{O}_3$
   

Q. A sample of element Y contains 250 atoms with a mass of 12 u and 50 atoms with a mass of 14 u. Calculate the average atomic mass of element X.

1. 12.33 g
2. 15.67 g
3. 10.28 g
4. 18.38 g

Q. The most abundant elements by mass in the body of a healthy human adult are oxygen (61.4%), carbon (22.9%), hydrogen (10.0%) and Nitrogen (2.6%). The weight which a $75\text{kg}$ person would gain if all the ${}^{1}H$ atoms are replaced by ${}^{2}H$ atoms is:

1. $15\text{kg}$
2. $37.5\text{kg}$
3. $7.5\text{kg}$
4. $10\text{kg}$

Q. A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g carbon dioxide, 0.690 g of water and no other products. A volume of 10.0 L (measured at STP) of this welding gas is found to weigh 11.6 g. Choose the correct molecular formula of the gas.

1. $C_2{H}_2$
2. $C_2{H}_4$
3. $C{H}_4$
4. $C_2{H}_6$

Q. The molecular mass of butyric acid was determined by experiment to be 88 $gmo{l}^{-1}$. What is the molecular formula?
Empirical formula=.$C_2{H}_{4}O$

1. $C_4{H}_8{O}_2$
2. $C_2{H}_{4}O$
3. $C{H}_{4}O$
4. $C_2{H}_4{O}_2$

Q.

Acetylene is the first member of a family of hydrocarbons called alkynes.
$H-C\equiv C-H$

What is its empirical formula?

1. $CH$

2. $C_2{H}_2$

3. $(CH{)}_2$

4. $(CH{)}_3$

Q. A hydrocarbon contains 17.2% of hydrogen and has a relative molecular mass of 58. Its molecular formula is:
(Given: Atomic masses of: C = 12 g, H = 1 g)

1. $C_2{H}_5$
2. $C_2{H}_4$
3. $C_4{H}_{10}$
4. $C_4{H}_8$

Q.

A hydrocarbon contains $86\%$ carbon, 488ml of the hydrocarbon weight 1.68 g at STP. Then the hydrocarbon is an

1. Alkane
2. Alkene
3. Alkyne
4. Arene

Q. A crystalline hydrated salt on being rendered anhydrous loses 45.6% of its weight.
The percentage composition of the anhydrous salt is:
$Al=10.5\%,K=15.1\%,S=24.8\%$ and oxygen $=49.6\%$
[Molar mass of $Al=27,K=39,S=32$].

What is the empirical formula of the hydrated salt?

1. $KAl{S}_2{O}_8.10H_{2}O$
2. $KAl{S}_2{O}_8.16H_{2}O$
3. $KAl{S}_2{O}_8.8H_{2}O$
4. $KAl{S}_2{O}_8.12H_{2}O$

Q. The ratio of mass percent of C and H in an organic compound $\left(C_x{H}_y{O}_z\right)$ is 6 : 1. If one molecule of the above compound $\left(C_x{H}_y{O}_z\right)$ contains half as much oxygen as it is required to burn one molecule of a compound $C_x{H}_y$ completely to $C{O}_2$ and $H_{2}O$, then the empirical formula of compound $C_x{H}_y{O}_z$ is:

1. $C_2{H}_4{O}_3$
2. $C_3{H}_6{O}_3$
3. $C_2{H}_{4}O$
4. $C_3{H}_4{O}_2$

Q. 5 g of compound A reacts with 10 g of compound B to produce a new compound C. What should be the mass of C according to law of conservation of mass?

1. 10 g
2. 5 g
3. 15 g
4. 50 g

Q. A given sample of pure compound contains $9.81\text{g}$ of $Zn$, $1.8\times {10}^{23}$ atoms of chromium and 0.60 mol of oxygen atoms. What is the simplest formula?

1. $ZnC{r}_2{O}_7$
2. $ZnC{r}_2{O}_4$
3. $ZnCr{O}_4$
4. $ZnC{r}_2{O}_6$

Q.

Calculate the number of aluminium ions present in $0.051\mathrm{g}$ of Aluminium oxide.

Q. An acid is a component of rancid butter and has a vile stench. Burning 0.44 g of the acid in excess oxygen yield 0.88 g of $C{O}_2$ and 0.36 g of $H_{2}O$ as the only products. Given that the acid contains only C, H, and O and if vapour density of the acid is 44, then which of the following options is not correct about it’s molecular formula?

1. It contains 4 carbon atoms
2. It contains 6 hydrogen atoms
3. It contains 2 oxygen atoms
4. Its empirical formula contains 2 carbon atoms

Q. A crystalline hydrated salt on being rendered anhydrous loses 45.6% of its weight.
The percentage composition of the anhydrous salt is:
$Al=10.5\%,K=15.1\%,S=24.8\%$ and oxygen $=49.6\%$
[Molar mass of $Al=27,K=39,S=32$].

What is the empirical formula of the salt?

1. $K_{2}Al{S}_2{O}_7$
2. $K_{2}A{l}_2{S}_2{O}_7$
3. $KAl{S}_2{O}_8$
4. $K_{3}Al{S}_2{O}_{12}$

Q. A hydrocarbon contains 17.2% of hydrogen and has a relative molecular mass of 58. Its molecular formula is:
(Given: Atomic masses of: C = 12 g, H = 1 g)

1. $C_2{H}_5$
2. $C_2{H}_4$
3. $C_4{H}_{10}$
4. $C_4{H}_8$

Q. A gaseous compound is composed of $85.7\%$ by mass carbon and $14.3\%$ by mass hydrogen. Its density is $2.5{\text{g L}}^{-1}$ and one mole of the gas occupies $44.8\text{L}$ of space at a particular temperature and pressure. Determine the molecular formula of the compound.

1. $C_2{H}_4$
2. $C_2{H}_2$
3. $C_4{H}_8$
4. $C_4{H}_{10}$

Q. 11.2 litre of a gas at STP weighs 14 g. The gas could not be

1. $N_2$
2. $CO$
3. $B_2{H}_6$
4. $N_{2}O$

Q. $5$ g of NaCl is dissolved in $1000$ g of water. If the density of the resulting solution is $0.997$ g per cc. Which of the following option(s) is/are correct?

1. Mole fraction of solute is $1.53\times {10}^{-3}$
2. Molarity of the solution is $0.085M$
3. Normality of the solution is $0.085N$
4. Molality of the solution is $0.854m$