Percentage Composition

Q.

Urea is a very important nitrogenous fertilizer. Its formula is $CO{N}_2{H}_4$. Calculate the percentage of carbon in urea.

(C = 12, O = 16, N = 14 and H = 1)

Q.

Calculate the percentage of oxygen in calcium hydroxide.

Q.

Calculate the percentage composition of each element in Potassium chlorate, $KCl{O}_3$

Q. Percentage of calcium in calcium nitrate is:

1. $48\%$
2. $40\%$
3. $28\%$
4. $24\%$

Q.

Complex A has a composition of ${\mathrm{H}}_{12}{\mathrm{O}}_6{\mathrm{Cl}}_3\mathrm{Cr}$. If the complex treatment with conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$loses $13.5\%$of its original mass, the correct molecular formula of A is: [Given: the atomic mass of $\mathrm{Cr}=52\mathrm{amu}\mathrm{and}\mathrm{Cl}=35\mathrm{amu}$].

1. $\left[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_5\mathrm{Cl}\right]{\mathrm{Cl}}_2.{\mathrm{H}}_2\mathrm{O}$

2. $\left[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_4{\mathrm{Cl}}_2\right]\mathrm{Cl}.2{\mathrm{H}}_2\mathrm{O}$

3. $\left[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_3{\mathrm{Cl}}_3\right].3{\mathrm{H}}_2\mathrm{O}$

4. $\left[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]{\mathrm{Cl}}_3$

Q.

Calculate the percentage of nitrogen in ammonium nitrate $\left({\mathrm{NH}}_4{\mathrm{NO}}_3\right)$.

Q. Chlorine has two isotopes, ${}_{17}^{35}\text{Cl}$ and ${}_{17}^{37}\text{Cl}$. Calculate the average atomic mass of chlorine atom (in a.m.u.) based on the given information.

$$\begin{array}{ccc}\text{S.No}& \text{Isotopes}& \text{Percentage abundance}\text{(\%)}\\ 1& {}_{17}^{35}\text{Cl}& 75\\ 2& {}_{17}^{37}\text{Cl}& 25\end{array}$$

1. 35.5

Q.

Estimate the amount of nitrogen present in urea?

1. 46

2. 85

3. 18

4. 28

Q.

Chlorine is made up of two isotopes, $\mathrm{Cl}-35(34.969\mathrm{u})$ and $\mathrm{Cl}-37(36.966\mathrm{u})$. Given chlorines atomic weight is $35.453\mathrm{u}$, what is the percent abundance of each isotope?

Q. Question 6(d)
Calculate the molar mass of the following substances:
(d) Hydrochloric acid, HCl

Q. Question 6(e)
Calculate the molar mass of the following substances:
(e) Nitric acid, $HN{O}_3$

Q. Caffeine (Mol. wt. = 194) contains 28.9% of nitrogen. How many number of nitrogen atoms are present in one molecule of caffeine?

1. 2
2. 5
3. 3
4. 4

Q. The average atomic mass of a sample of an element ${}^{\prime }{X}^{\prime }$ is $16$. What are the $\%$ of isotopes ${}_8^{16}X$ and ${}_8^{18}X$ in the sample?

1. $80\%$ and $20\%$
2. $90\%$ and $10\%$
3. $70\%$ and $30\%$
4. $40\%$ and $60\%$

Q. Calculate the molecular mass of $H_{2}O$ (Water)

1. $18$
2. $20$
3. $36$
4. $16$

Q.

Percentage composition of a compound is the percentage by___of each element present in it.

1. Density

2. None of the above

3. Volume

4. Weight

Q. How many gram molecules of ammonia are present in 100 grams of ammonia? [2 marks]

Q. Calculate the molecular mass of the following substances:

(a) Ethyne $\left(C_2{H}_2\right)$

(b) Sulphur molecule $\left(S_8\right)$

(c) Phosphorus molecule $\left(P_4\right)$

(d) Hydrochloric acid $\left(HCl\right)$

(e) Nitric acid $\left(HN{O}_3\right)$

Q. Read the given statements carefully.

नीचे दिये गये कथनों को सावधानीपूर्वक पढ़िए।

(a) The difference between the molecular mass of ethyne and ammonia is 11 u

(a) एथाइन तथा अमोनिया के आणविक द्रव्यमान में अंतर 11 u होता है

(b) The ratio of the formula unit mass of sodium oxide and calcium oxide is 31 : 28

(b) सोडियम ऑक्साइड तथा कैल्सियम ऑक्साइड के सूत्र इकाई द्रव्यमान का अनुपात 31 : 28 होता है

(c) The ratio of the mass of anion to that of cation in a molecule of magnesium sulphide is 3 : 4

(c) मैग्नीशियम सल्फाइड के एक अणु में ऋणायन व धनायन का द्रव्यमान अनुपात 3 : 4 होता है

(d) The difference between the molecular mass of ammonium sulphate and sodium carbonate is 26 u

(d) अमोनियम सल्फेट व सोडियम कार्बोनेट के आणविक द्रव्यमान में अंतर 26 u होता है

(e) The chemical formula and molecular mass of nitric acid is HNO₃ and 63 u respectively

(e) नाइट्रिक अम्ल का रासायनिक सूत्र तथा आणविक द्रव्यमान क्रमशः HNO₃ तथा 63 u होता है

The correct statements are

सही कथन हैं

1. (b), (d) and (e)
   
   (b), (d) तथा (e)
2. (a), (d) and (e)
   
   (a), (d) तथा (e)
3. (a), (b), (c) and (e)
   
   (a), (b), (c) तथा (e)
4. All (a), (b), (c), (d) and (e)
   
   सभी (a), (b), (c), (d) तथा (e)

Q. The smallest particle of a substance (element or compound) which has the properties of that substance and can exist independently is called a ..............

1. Nucleus
2. Molecule
3. Atom
4. Neutrons

Q. Question 10
If 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 bromine atom.

Q.

Two oxides of a metal contain $50\%$ and $40\%$ of the metal, respectively. The formula of the first oxide is $\mathrm{MO}$. Then, the formula of the second oxide is

1. ${\mathrm{MO}}_2$

2. ${\mathrm{M}}_2\mathrm{O}$

3. ${\mathrm{M}}_2{\mathrm{O}}_5$

4. ${\mathrm{M}}_2{\mathrm{O}}_3$

Q. Chlorine has two isotopes, ${}_{17}^{35}\text{Cl}$ and ${}_{17}^{37}\text{Cl}$. Calculate the average atomic mass of chlorine atom (in a.m.u.) based on the given information.

$$\begin{array}{ccc}\text{S.No}& \text{Isotopes}& \text{Percentage abundance}\text{(\%)}\\ 1& {}_{17}^{35}\text{Cl}& 75\\ 2& {}_{17}^{37}\text{Cl}& 25\end{array}$$

1. 35.5

Q. A certain sample of element X contains 60% of ${}^{69}X$ and 40% of ${}^{71}X$. What is the average atomic mass of element Z in this sample?

1. 69.2
2. 69.8
3. 70.0
4. 70.2

Q.

One mole of oxygen atom weighs 16 grams, what will be the mass (in grams) of 0.4 moles of oxygen atoms?

1. ¹/₄ mole

2. 640 mole

3. 0.4 mole

4. 4 mole

Q. Calculate the percentage composition of the different atoms in one mole potassium chlorate.

Q.

The mass percentage of nitrogen in urea ($N{H}_{2}CON{H}_2$)is:

1. 
2. 
3. 
4. 

Q. What is the % of $H_{2}O$ in $Fe(CNS{)}_3.3H_{2}O$

1. 45
2. 30
3. 19
4. 25

Q.

Calculate the percentage of phosphorus in :

(a) Calcium hydrogen phosphate Ca$(H_{2}P{O}_4{)}_2$

(b) Calcium phosphate $C{a}_3(P{O}_4{)}_2$

Q. Find the temperature at which most probable speed of He gas has the same value of root mean square speed of O₂ molecule at 300 K.

वह ताप ज्ञात कीजिए जिस पर He गैस की प्रायिकता चाल का मान 300 K पर O₂ अणु के वर्ग माध्य मूल चाल के मान के समान है।

1. 56.25ºC
2. 56.25 K
3. 900 K
4. 300 K

Q. Given that the abundance of isotopes ${}^{54}Fe{,}^{56}Fe,$ and ${}^{57}Fe$ is 5%, 90% and 5%, respectively. The atomic mass of Fe is
(IIT-JEE, 2009)

1. 55.85
2. 55.95
3. 55.75
4. 55.05