Empirical & Molecular Formula

Q.

Maximum number of atoms are present in

1. 11.2 litres of $S{O}_2$ at STP

2. 22.4 litres of Helium at STP

3. 2.0 g. of hydrogen

4. 11.2 litres of methane at STP

Q.

1.615 g of anhydrous $ZnS{O}_4$ was places in moist air. After a few days, its mass was found to be 2.875g. The molecular formula for hydrated zinc sulphate is

1. 
2. 
3. 
4. 

Q.

Calculate the following in 5.6g of nitrogen

a) Number of moles of N_2.

b) Number of molecules of N₂.

c) Number of atoms of nitrogen.

Q.

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

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

Q. If a bromine atom is available in the form of say two isotopes ${}_{35}^{79}Br$(49.7%) and ${}_{35}^{81}Br$ (50.3%), calculate the average atomic mass of the bromine atom.

Q.

What are the two types of chemical formulae?

Q. How much calcium oxide will be formed on decomposition of $350\text{g}$ of limestone.
(Given: Atomic mass of $Ca=40u$)

1. $224\text{g}$
2. $220\text{g}$
3. $196\text{g}$
4. $320\text{g}$

Q. The simplest formula of a compound containing 50% of an element $X$ (atomic mass = 10) and 50% of the element $Y$ (atomic mass = 20) is:

1. $XY$
2. $X_{2}Y$
3. $X_2{Y}_2$
4. $X_2{Y}_3$

Q. A hydrocarbon contains $82.8\%$ of carbon. Its molecular formula if its vapour density is $29$ is :

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

Q. Which of the following is the correct chemical formula of magnesium hydroxide?

1. Mg$(OH{)}_2$
2. MgOH
3. MgO$H_2$
4. $M{g}_{2}O{H}_2$

Q.

A- flask contains 3.2 g of sulphur dioxide. Calculate the following (i) the moles of sulphur dioxide present in the flash (ii) the number of molecules of sulphur dioxide present in the flask.

Q. If two compounds have the same empirical formula but different molecular formula, they must have :

1. different percentage composition
2. different molecular weights
3. same vapour density
   
4. none of these

Q. What is the empirical formula of vanadium oxide, if 2.74 g of metal oxide contains 1.53 g of metal?

1. $V_2{O}_3$
2. VO
3. $V_2{O}_5$
4. $V_2{O}_7$

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 gaseous hydrocarbon has 85% carbon and vapour density of 28. The possible molecular formula of the hydrocarbon will be :

1. $C_3{H}_6$
2. $C_2{H}_4$
3. $C_4{H}_8$
4. $C_5{H}_{12}$

Q. A compound made up of two elements $A$ and $B$ is found to contain $25$% $A$ (atomic mass $=12.5$) and $75$% of $B$ (atomic mass $=37.5$). The simplest formula of the compound is:

1. $AB$
2. $A_{3}B$
3. $A{B}_2$
4. $A{B}_3$

Q. Calculate the number of moles of ethylene required to produce $44$g of carbon dioxide gas on its complete combustion.

1. 4.4
2. 1
3. 2
4. 0.5

Q. 0.15 g of a hydrocarbon upon combustion gave 0.44 g of carbon dioxide and 0.27 g of water. If the vapour density of the hydrocarbon is 15, find out its molecular formula.

1. $C_2{H}_4$
2. $C_3{H}_8$
3. $C_2{H}_6$
4. $C{H}_4$

Q. Give the formula of sodium bisulphate.

Q.

A compound has an empirical formula of C₂HBr. If the molar mass of the compound is 314.7 g/mol, what is the molecular formula of the compound? (Atomic mass of Br = 80g/mol)

Q. Choose the option that depicts the correct order of molecular mass of the given compounds.​
NaO, NaOH, NaCl

1. NaO < NaCl < NaOH​
2. NaOH < NaO < NaCl​
3. NaOH < NaCl < NaO​
4. NaO < NaOH < NaCl​

Q. $I$. A $14.5g$ sample of a compound which contains sulfur and chlorine is found to contain $4.5g$ of sulfur and $10g$ of chlorine. The molecular formula of the compound could be $S{Cl}_2$.
$II$. The mass ratio of sulfur to chlorine in the sample is $1:2$.

1. Statement $I$ is false, Statement $II$ is true
2. Statement $I$ is false, Statement $II$ is false
3. Statement $I$ is true, Statement $II$ is false
4. Statement $I$ is true, Statement $II$ is true

Q. From the recorded data:
Weight of U-tube_____$20.36$g
Weight of U-tube and calcium chloride before______$39.32$g
Weight of U-tube and calcium chloride after______$57.32$g
Weight of boat and contents(copper oxide)before_____$30.23$g
Weight of boat and contents after________$14.23$g
Weight of boat_______$5.00$g
What conclusion can be derived from the data collected?

1. Oxygen was lost from the $CaC{l}_2$
2. Oxygen was generated in the U-tube
3. Water was formed from the reaction
4. Hydrogen was absorbed by the $CaC{l}_2$
5. CuO was formed in the decomposition

Q. The approximate production of sodium carbonate per month is $424\times {10}^{6}g$ while that of methyl alcohol is $320\times {10}^{6}g$. Which of the following is produced more in terms of number of moles?

1. Methyl alcohol
2. Sodium carbonate
3. Data insufficient
4. Both (A) and (B)

Q. The simplest formula of a compound containing 50% of element $X(atomicmass=10)$ and 50% of the element $Y(atomicmass=20)$ by weight is :

1. $X_{2}Y$
2. $X{Y}_2$
3. $XY$
4. $X_2{Y}_3$

Q. Which of the following contains maximum number of molecules?

1. 1 gm of $C{O}_2$
2. 1 gm of $N_2$
3. 1 gm of $H_2$
4. 1 gm of $C{H}_4$

Q. $12g$ of $Mg$ (at. mass $24$) will reaction completely with acid to give:

1. $1/2mole$ of $H_2$
2. $2/3mole$ of $O_2$
3. both $1/2mole$ of $H_2$ and $1/2mol$ of $O_2$
4. one mole of $H_2$

Q. What is the mole fraction of glycerin $C_3{H}_5(OH{)}_3$ in a 100 g solution containing 33 g of glycerin, 60 g isopropyl alcohol and rest water?

1. 0.359
2. 0.258
3. 0.205
4. 0.480

Q. What is the percent composition by weight of $Al$ in ${{Al}_2\left({SO}_4\right)}_3$?

1. 7.9%
2. 31.6%
3. 15.8%
4. 12.7%

Q. Which of these is not a molecule?

1. $Cl$
2. $O_3$
3. $NaCl$
4. $H_2$