ADDITIONAL QUESTIONS FOR PRACTICE
I. VERY SHORT ANSWER QUESTIONS [1MARK]
- Name the scientist who laid the foundation of chemical sciences. How?
- Define law of conservation of mass.
- Define law of constant proportion.
- Which organisation approves the names of elements all over the world? Write the symbol of gold.
- Write the symbols of tungsten and iron.
- Name the element which is used as the reference for atomic mass.
- ‘Atoms of most elements are not able to exist independently’. Name two atoms which exist as independent atoms.
- What is the number of electrons in Mg atom and Mg+2ion?
- Which of the following species is electrically neutral and why?
Na+, Cl–, K+, Na, Ca+2
- Define atomicity.
- Write atomicity of the following:
(i) Sulphur, (ii) Phosphorus
- What are polyatomic ions ? Give two examples.
- What is the atomicity of Argon ?
- Give one relevant reason why scientists choose 1/16 of the mass of an atom of naturally occurring oxygen as the atomic mass unit.
- State the number of hydrogen atoms in 1 g of hydrogen.
- What is molar mass? What are its units?
- Define atomic mass unit.
- The relative atomic mass of oxygen atom is 16. Explain its meaning.
- Distinguish between molecular mass and molar mass.
- Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass ?
- Which postulate of Dalton’s atomic theory can explain the law of definite proportions ?
- Why is it not possible to see an atom with naked eyes?
- What is meant by the term chemical formula?
- How many atoms are present in a (i) H2S molecule and (ii)PO43– ion ?
II. SHORT ANSWER QUESTIONS [2MARKS]
- Name the scientists whose experimentation established laws of chemical combination. Name the laws also.
- Give two drawbacks of Dalton’s atomic theory.
- Calculate molar mass of sulphuric acid.
- Give the electronic configuration of:
(i) Al atom and its ion (ii) O atom and its ion
- Give one example each of (i) Monovalent cation (ii) Bivalent cation (iii) Monovalent anion (iv) Bivalent anion
- How would you differentiate between a molecule of element and a molecule of compound? Write one example of each type.
- What is meant by a chemical formula? Give examples.
- What is meant by a molecule ? Give examples.
- Define one mole, illustrate its relationship with Avogadro constant.
- Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas ?
- Write down the formula of :
(i) Sodium oxide (ii) Aluminium chloride (iii) Sodium sulphide (iv) Magnesium hydroxide
- When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen ? Which law of chemical combination will govern your answer ?
- What are polyatomic ions ? Give examples.
- Give the names of the elements present in the following compounds:
(a) Quicklime (b) Hydrogen bromide (c) Baking powder (d) Potassium sulphate.
- What is the mass of:
(a) 0.2 mole of oxygen atoms ?
(b) 0.5 mole of water molecules ?
III. SHORT ANSWER QUESTIONS [ 3 MARKS]
- Write the chemical symbols of two elements:
(i) Which are formed from the first letter of the elements’ name ?
(ii) Whose names have been taken from the names of the elements in Latin ?
(iii) Which are formed from the first two letters of the elements’ name ?
- Write the correct symbols of the following elements which are written incorrectly.
(i) FE (Iron) (ii) AL (Aluminium) (iii) CO (Cobalt) (iv) AG (silver) (v) NA (sodium) (vi) AR (Argon)
- State two examples in each case and write their chemical formulae:
(a) Molecules having (same kind of atoms only)
(b) Molecules having two different kinds of atoms.
(c) Molecules having three different kinds of atoms.
- State what are ions. Write the formulae of two divalent cations and anions each.
- Classify the following compounds diatomic, triatomic and polyatomic molecules:
HCl, H2, H2O, NH3, CH3OH, PCl5.
- Write the names of the following compounds:
(a) NiS (b) Mg (NO3)2 (c) Na2SO4 (d) Al (NO3)3 (e) K3PO4 (f) Ca3N2
- Write the chemical names of the following compounds:
(a) K2SO4 (b) Mg3(PO4)2 (c) NH4Cl (d) ZnS (e) Na3N (f) AgBr
- In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass,
- Write down the names of compounds represented by the following formulae:
(i) Al2(SO4)3 (ii) CaCl2 (iii) K2SO4 (iv) KNO3 (v) CaCO3 (vi) Ca (HCO3)2
- Calculate the formula unit masses of ZnO, Na2O, K2CO3, given atomic masses of Zn = 65u, Na = 23u, K = 39 u, C =3 12 u, and O = 16 u.
- If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
- A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.
- Write the chemical formulae of the following:
(a) Magnesium chloride (b) Calcium oxide (c) Copper nitrate (d) Aluminium chloride
(e) Calcium carbonate (f) Ammonium hydroxide
- What is the mass of:
(a) 1 mole of nitrogen atoms ?
(b) 4 moles of aluminium atoms (Atomic mass of aluminium = 27) ?
(c) 10 moles of sodium sulphite (Na2SO3) ?
- Convert into mole. (a)12 g of oxygen gas (b) 20 g of water (c) 22 g of carbon dioxide.
- Calculate the number of molecules of sulphur (S8) present in 16 g of solid sulphur.
- Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.(Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass of Al = 27 u).
- When 3.0 g of magnesium is burnt in 2.00 g of oxygen, 5.00 g of magnesium oxide is produced. What mass of magnesium oxide will be formed when 3.00 g magnesium is burnt in 5.00 g of oxygen? Which law of chemical combination will govern your answer ? State the law.
- State the law of conservation of mass. Is this law applicable to the chemical reactions? Elaborate your answer with the help of an example.
- A sample of vitamin C is known to contain 2.58 × 1024 oxygen atoms. How many moles of oxygen atoms are present in the sample ?
- Sidak took 5 moles of carbon atoms in a container and Sehaj also took 5 moles of sodium atoms in another container of the same weight, (a) Whose container is heavier? (b) Whose container has more number of atoms?
- Fill in the missing data in the table:
|No. of moles||2||—||—||0.5|
|No. of particles||—||3.011 ×1023||—||—|
- The visible universe is estimated to contain 1022 stars. How many moles of stars are present in the visible universe?
- The formula unit of mass of Na2O is 62 U. Calculate the atomic mass of sodium (Na).
(Given atomic mass of oxygen = 16)
- What are ionic and molecular compounds ? Give examples.
- (a) Why does not atomic mass of an element represent the actual mass of its atom ?
(b) “The atomic mass of an element is in fraction.” What does it mean ?
- Explain why the number of atoms in one mole of hydrogen gas is double the number of atoms in one mote of Helium gas ?
- Why atoms form ions ?
- Write three points of difference between an atom and a molecule.
What is the difference between an atom and a molecule ?
- Define formula unit mass. Calculate formula unit mass of NaCI (Atomic mass of Na = 23 u,
Cl = 35.5 u)
- (a) Give an example in each of the following cases:
(i) a divalent anion, (ii) a trivalent cation. (iii) a monovalent anion.
(b) Calculate the mass of the following:
(i) 2 moles of carbon dioxide, (ii) 6.022 × 1023 molecules of carbon dioxide.
- (a) Write the chemical formulae of the following:
(i) Calcium oxide, (ii) Magnesium chloride, (iii) Aluminium hydroxide
(b) Calculate the number of molecules of sulphur (•%) present in 128 g of solid sulphur.
(Atomic mass S = 32 u)
III. LONG SHORT ANSWER QUESTIONS [ 5 marks]
- Give the postulates of Dalton’s atomic theory.
- (a) Give one point of difference between an atom and an ion.
(b) Give one example each of a polyatomic cation and an anion.
(c) Identify the correct chemical name of FeSO3: Ferrous sulphate. Ferrous sulphide, Ferrous sulphite.
(d) Write the chemical formula for the chloride of magnesium.
- (a) Define: (i) Molecular mass, (ii) Avogadro constant.
(b) Calculate the number of molecules in 50 g of CaCO3.
(Atomic mass of Ca = 40 u, C = 12 u and 0 u)
(c) If one mole of sodium atom weighs 23 g, what is the mass (in g) of one atom of sodium ?
- Calculate the molecular masses of H2 , O2, Cl2, CO2, CH4, C2H6, C2H4,NH3, CH3OH,H2S.
- Calculate the molar mass of the following substances:
(a) Ethyne, C2H2
(b) Sulphur molecule,S8
(c) Phosphorus molecule, P4 (Atomic mass of phosphorus = 31)
(d) Hydrochloric acid, HCI (e) Nitric acid, HNO3
IV. NUMERICAL PROBLEMS
- Calcium chloride when dissolved in water dissociates into its ions according to the following equation:
Calculate the number of ions obtained from CaCl2 when 222 g of it is dissolved in water.
- The difference in the mass of 100 moles each of sodium atoms and sodium ions is 5.48002 g. Compute the mass of an electron.
- Cinnabar (HgS) is a prominent ore of mercury. How many grams of mercury is present in 225 g of pure
HgS ? Molar mass of Hg and S are 200.6 g
and 32 g
- The mass of one steel screw is 4.11 g. Find the mass of one mole of these steel screws. Compare this value with the mass of the earth (5.98 × 1024kg). Which one of the two is heavier and by how many times ?
- Compute the difference in masses of 10:* moles each of magnesium atoms and magnesium ions.
(Mass of an electron = 9.1 ×
- Which has more number of atoms ? (i) 100 g of W2 or (ii) 100 g of NH3
- Compute the number of ions present in 5.85 g of sodium chloride.
- A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present in one gram of this sample of gold ?
- Compute the difference in masses of one mole each of aluminium atoms and one mole of its ions. (Mass of an electron is 9.1 ×
g). Which one is heavier ?
- A silver ornament of mass ‘m’ gram is polished with gold equivalent to 1 % of the mass of silver. Compute the ratio of the number of atoms of gold and silver in the ornament.
- A sample of ethane (C2H6) gas has the same mass as 1.5 × 1020 molecules of methane (CH4). How many C2H6 molecules does the sample of gas contain ?
(a) Calculate the number of molecules of SO2 present in 44 g of it.
(b) If one mole of oxygen atoms weighs 16 grams, find the mass of one atom of oxygen in (grams).
- Sodium is represented as
(a) What is its atomic mass ?
(b) Write its gram atomic mass.
(c) How many atoms of Na will be there in 11.5 g of the sample ?