Chemistry

Atoms and Molecules

Question:

Work out the formula for magnesium hydrogencarbonate.

Answer:

Mg(HCO3)2
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Atoms and Molecules

Q 1.

Write the full form of IUPAC.

Q 2.

Calculate the number of molecules of phosphorus (P4) present in 31 gram of phosphorus.

Q 3.

Name the following compounds. Also write the symbols/formulae of the ions present in them :
(a) CuSO4
(b) (NH4)2SO4
(c)Na2O
(d)Na2CO3
(e)CaCl2

Q 4.

How many moles are there in 34.5 g of sodium ? (Atomic mass of Na = 23 u)

Q 5.

Calculate the mass in grams of 0.17 mole of hydrogen sulphide, H2S.

Q 6.

(a) What is meant by 'a mole of carbon atoms' ?
(b)(b) Which has more atoms, 50 g of aluminium or 50 g of iron ? Illustrate your answer with the help of calculations.
(Atomic masses : A1 = 27 u ; Fe = 56 u)

Q 7.

What are the laws of chemical combinations?

Q 8.

Who established the two important laws of chemical combinations?

Q 9.

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?

Q 10.

Fill in the blanks:
_________ are building block of all matter.

Q 11.

Name the element having following Latin names
(i) Stibium
(ii) Cuprum
(iii) Argentum
(iv) Natrium
(v) Stannum
(vi) Wolfram
(vii) plumbum
(viii) Kalium

Q 12.

(i) What is the chemical formula of Water molecule?
(ii) What is its atomicity?
(iii) Calculate the ratio of masses of atoms of elements present in water molecule.
(iv) Calculate the ratio by number of atoms of elements present in water molecule.

Q 13.

What are the building blocks of matter ?

Q 14.

Fill in the following blanks with suitable words :
(a) In water, the proportion of oxygen and hydrogen is............by mass.
(b) In a chemical reaction, the sum of the masses of the reactants and the products remains

Q 15.

What is meant by atomicity ? Explain with two

Q 16.

Calculate the molecular masses of the following compounds :
(a) Methane, CH4
(b) Ethane, C2H6 © Eathen C2H4 (d) Ethyne C2H2
(Atomic masses : C=12 U;H=1 U)

Q 17.

Calculate the molecular mass of ethanoic acid, CH3COOH.
(Atomic masses :C = 12u;H = lu;0 = 16u)

Q 18.

Calculate the molecular mass of nitric acid,HNO3.
(Atomic masses :H =lu; N = 14u;0 = 16u)

Q 19.

Calculate the molecular masses of the following compounds :
(a) Hydrogen sulphide, H2S
(b) Carbon disulphide, CS2
(Atomic masses :H = lu;S = 32u;C = 12u)

Q 20.

State whether the following statements are true or false :
(a)A sodium ion has positive charge because it has more protons than a neutral atom
(b)A chloride ion has negative charge because it has more electrons than a neutral atom.

Q 21.

Fill in the following blanks with suitable words :
(a)The particle which is formed by the gain of electrons by an atom is called...........
(b)The particle which is formed by the loss of electrons by an atom is called............
(c)The particle which is formed by the loss or gain of electrons by an atom is called..........
(d)A potassium ion has positive charge because it contains less...........than...........
(e) A sulphide ion has negative charge because it contains less...........than..........

Q 22.

What is an ion ? How is an ion formed ? Explain with the help of two examples of different ions.

Q 23.

What is the difference between a cation and an anion ? Explain with examples. Using this information, write down the formulae of:
(i) Sodium sulphide
(ii) Copper nitrate

Q 24.

How many atoms are present in one gram atomic mass of a substance ?

Q 25.

What is the mass of 0.2 mole of oxygen atoms ?

Q 26.

Find the mass of 2 moles of nitrogen atoms.

Q 27.

If 16 g of oxygen contains 1 mole of oxygen atoms, calculate the mass of one atom of oxygen.

Q 28.

Calculate the mass m grams of 0.17 mole of hydrogen sulphide, H,S.(Atomic masses : H = 1 U/ S = 32 u)

Q 29.

(a) Define gram molecular mass of a substance. How much is the gram molecular mass of oxygen ?
(b) If sulphur exists as S8 molecules, calculate the number of moles in 100 g of sulphur.. (S = 32 u)

Q 30.

Give an example to show Law of conservation of mass applies to physical change also.

Q 31.

State Law of constant proportions. Explain with an example.

Q 32.

What are the postulates of Dalton's atomic theory?

Q 33.

Fill in the blanks:
Atoms can be observed using ____________ Microscope.

Q 34.

Fill in the blanks:
The chemical symbol of flourine is ________.

Q 35.

Write down the names of compounds represented by the following formulae:

(i) Al2(SO4)3
(ii) CaCl2
(iii) K2SO4
(iv) KNO3
(v) CaCO3

Q 36.

How many atoms are present in a
(i) H2S molecule and
(ii) PO43- ion?

Q 37.

What is the molecular mass of a substance?

Q 38.

Calculate the molecular masses of H2, O2, Cl2, CO2, CH4, C2H6, C2H4, NH3, CH3OH.

Q 39.

Calculate the formula unit masses of ZnO, Na2O, K2CO3, given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u.

Q 40.

What are ionic compounds?

Q 41.

Name one element each which forms diatomic and tetra atomic molecule.

Q 42.

What is molar mass?

Q 43.

Who introduced the term 'mole' in chemistry?

Q 44.

How many moles are there in 4.6 gms of Sodium(Na)?

Q 45.

Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given, atomic mass of Na = 23 u, Fe = 56 u)?

Q 46.

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)?

Q 47.

Calculate the molecular masses of the following :
(a) Hydrogen, H2 (b) Oxygen O2 © Chlorine Cl2 (d) Ammonia NH3 (e) Carbon dioxide, CO2
(Atomic masses : H=1 U;O=16 U; Cl=35.5 U;N=14 U;C=12 U)

Q 48.

What do we call those particles which are formed :
(a)by the gain of electrons by atoms ?
(b)by the loss of electrons by atoms ?

Q 49.

Name the elements water is made of. What are the valencies of these elements ? Work out the chemical formula for water.

Q 50.

An element X has a valency of 4 whereas another element Y has a valency of 1. What will be the formula of the compound formed between X and Y ?