Empirical & Molecular Formula

Q.

The ratio of the mass of C-12 atom to that of an atom of element $X$ (whose atomicity is four) is 1 : 9. Themolecular mass of element $X$ is

1. 

2. 

3. 

4. 

Q.

Where can formula mass be applicable?

Q.

Calculate the molecular formula of a compound whose empirical formula is ${\mathrm{CH}}_2\mathrm{O}$ and vapour density is 30.

Q.

The formula of exhausted permutit is :

1. CaAl2Si2O8xH2O

2. Na2Al2Si2O8.xH2O

3. CaB2Si2O8.xH2O

4. K2Al2Si2O8.xH2O

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. 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.

10 ml of gaseous hydrocarbon on combustion gives 40 ml of $C{O}_2$(g) and 50 ml of$H_{2}O$ (vap.). The hydrocarbon is

1. C₈H₁₀

2. C₄H₈

3. C₄H₁₀

4. C₄H₅

Q.

The simplest formula of a compound containing $50\%$ of element X (atomic mass 10) and $50\%$ of element Y (atomic mass 20) is

1. $XY$
2. $X_{2}Y$
3. $X{Y}_3$
4. $X_2{Y}_3$

Q. A substance on analysis gave the following percentage composition: $Na=43.4\%,C=11.3\%$ and $O=45.3\%$. Calculate the empirical weight (Atomic weight in amu of $Na=23,C=12,O=16$).

Q.

$K_{sp}$ of $BaCr{O}_4$ is $2\times {10}^{-10}$ at room temperature. Calculate the mass of Barium chromate lost by washing with three litres of water. Will the loss in mass depend on the quantity of precipitate?

1. 10.625 mg

2. 3.88 mg

3. 15.6 mg

4. 5.64 mg

Q. A sample of a pure compound contains $9.81\text{gm}$ of $Zn$, $1.8\times {10}^{23}$ atoms of chromium and $0.60$ mole of oxygen atoms. What is its simplest formula?

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

Q.

Heavy water is chemically identical to $H_{2}O$ - True or False?

1. True

2. False

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. During an analysis of $255\text{mg}$ of a molecule that contains only $C,H$ and $O$, $561\text{mg}C{O}_2$ is produced along with $306\text{mg}{H}_{2}O$ on combustion. If the molar mass of the compound is $180\text{g/mol}$, what is the molecular formula of the compound ?

1. $C_{16}{H}_4{O}_9$
2. $C_{10}{H}_{21}{O}_9$
3. $C_5{H}_{21}{O}_3$
4. $C_9{H}_{24}{O}_3$

Q. Element Y has second valence shell, and it can form a stable compound with element X_{11. }If the formula of the compound is X_2Y , what is the atomic number of Y ?

Q.

Two oxides of a metal contain $27.6\%and30.0\%$ of Oxygen, respectively. If the formula of the first be $M_3$$O_4$. Find that of the second.

1. $M_3$$O_5$

2. $M_3$$O_3$

3. $M_3$O${}_2$

4. $M_2$$O_3$

Q. A $2.8g$ of mixture of carbonates of two monovalent metals are heated to corresponding oxides and carbondioixde. The metal $A$ is $20\%$ by weight. The mass of carbondioxide obtained from the reaction is $0.88g$. The mass of the metal $B$ in the mixture is

1. $2.08g$
2. $0.56g$
3. $1.04g$
4. $1.2g$

Q. If in alkane molecule there is $n$ carbon atom, then the number of corresponding hydrogen atom can be given as:

1. $2n-2$
2. $n$
3. $2n$
4. $2n+2$

Q. A gaseous mixture of $H_2$ and $C{O}_2$ gas contains $66$ mass $\%$ of $C{O}_2$ . The vapour density of the mixture is

1. $6.1$
2. $5.4$
3. $2.7$
4. $10.8$

Q.

what do we mean by transition ?

Q.

What is the mass of a formula unit of ${\mathrm{Na}}^{+}{\mathrm{Cl}}^{-}$( atomic mass of $\mathrm{Na}=23,\mathrm{Cl}=35.5$)?

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 certain alkaloid has $70.8\%C,6.2\%H$ and $4.1\%$ of N and rest O. The empirical formula is

1. $C_{20}{H}_{21}N{O}_4$
2. $C_{20}{H}_{20}N{O}_4$
3. $C_{21}{H}_{20}N{O}_3$
4. $C_{20}{H}_{10}N{O}_3$

Q.

The empirical formula mass of a compound is one-sixth of its molecular mass. What is the molecular formula corresponding to that substance?

1. ${\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}$

2. ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$

3. ${\mathrm{C}}_2{\mathrm{H}}_4{\mathrm{O}}_3$

4. ${\mathrm{C}}_3{\mathrm{H}}_6{\mathrm{O}}_2$

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. 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. $180\text{g}$ of a compound containing $C,H$ and $O$ reacts fully with excess oxygen and produces $264\text{g}$ of $C{O}_2$ and $108\text{g}$ of $H_{2}O$. If the ratio of molar mass of the compound to the empirical formula mass is $6$ then find the molecular formula of given compound.

1. $C{H}_{2}O$
2. $C_6{H}_{12}{O}_6$
3. $C_{12}{H}_{24}{O}_{12}$
4. $C_{42}{H}_{84}{O}_{42}$