Atoms and Molecules Science - Atoms and Molecules

If 1.4g of calcium oxide is formed by the complete decomposition of calcium carbonate, then the amount of calcium carbonate taken and the amount of carbon dioxide formed will be respectively:

1. 2.2g and 1.1g
2. 1.1g and 2.5g
3. 2.5g and 1.1g
4. 5.0g and 1.1g

The atomic number of an element E is 16. The number of electrons in ion E^2- will be:

1. 16
2. 18
3. 15
4. 14

The anion of an element has:

1. More electrons than the normal atom.
2. Less electrons than the normal atom.
3. More protons than the normal atom.
4. Same number of electrons as normal atom.

The Latin language name of an element is natrium. The English name of this element is:

1. Sodium.
2. Potassium.
3. Magnesium.
4. Sulphur.

The atoms of which of the following pair of elements are most likely to exist in free state?

1. Hydrogen and helium.
2. Argon and carbon.
3. Neon and nitrogen.
4. Helium and neon.

In a chemical reaction, the sum of the masses of the reactants and the products remains unchanged. This is called _________.

The particle which is formed by the loss of electrons by an atom is called _________.

The particle which is formed by the gain of electrons by an atom is called _________.

In water, the proportion of oxygen and hydrogen is _________ by mass.

A potassium ion has positive change because it contains less _________ than __________.

A sodium ion has positive charge because it has more protons than a neutral atom.

A chloride ion has negative charge because it has more electrons than a neutral atom.

An element Y has a valency of 4. Write the formula for its:

1. Chloride.
2. Oxide.
3. Sulphate.
4. Carbonate.
5. Nitrate.

Name the elements represented by the following symbols:
Hg, Pb, Au, Ag, Sn.

Work out the formulae for the following compounds:
Sodium oxide.

Write the full form of IUPAC.

Find the mass of 2 moles of oxygen atoms?

The valencies (or charges) of some of the ions are given below:

Ion	Valency(Charges)	Ion	Valency(Charge)
Sodium ion	1+	Bromide ion	1-
Ammonium ion	1+	Hydroxide ion	1-
Calcium ion	2+	Sulphate ion	2-
Lead ion	2+	Phosphate ion	3-

Using this information, write down the formulate of the following compounds:

1. Sodium phosphate.
2. Ammonium sulphate.
3. Calcium hydroxide.
4. Lead bromide.

Calculate the molar masses of the following substances. Write the results with proper units.

1. Ozone molecule, O₃
2. Ethanoic acid, CH₃COOH

Explain the formation of (i) sodium ion, and (ii) chloride ion, form their respective atoms giving the number of protons and number of electrons in each one of them. What is the reason for positive charge on a sodium ion and a negative charge on a chloride ion?

What is the difference between the molecule of an element and the molecule of a compound? Give one example of each.

Calculate the formula masses of the following compounds:

1. Calcium chloride
2. Sodium carbonate

(Given: Atomic masses: Ca = 40u; Cl = 35. 5u; Na = 23u; C = 12u; O = 16u)

Calculate the molecular masses of the following:

1. Hydrogen, H₂
2. Oxygen, O₂
3. Chlorine, Cl₂
4. Ammonia, NH₃
5. Carbon dioxide, CO₂

(Atomic masses: H = 1 u; O = 16 u; Cl = 35.5 u; N = 14 u; C = 12 u)

What is the number of zinc atoms in a piece of zinc weighing 10g?
(Atomic mass of Zn = 65u)

Calculate the molecular masses of the following compounds:

1. Methane, CH₄
2. Ethane, C₂ H₆
3. Ethene, C₂ H₄
4. Ethyne, C₂ H₂

(Atomic masses: C = 12u; H = 1u)

An element A forms an oxide A₂O₅.

1. What is the valency of element A?
2. What will be the formula of chloride of A?

If the aluminium salt of an anion X is Al₂X₃, what is the valency of X? What will be the formula of the magnesium salt of X?

In an experiment, 4.90g of copper oxide was obtained form 3.92g of copper. In another experiment, 4.55g of copper oxide gave, on reduction, 3.64g of copper. Show with the help of calculations that these figures verify the law of constant proportions.

Name the following compounds. Also write the symbols/ formulae of the ions present in them:

1. CuSO₄
2. (NH₄)₂SO₄
3. Na₂O
4. Na₂CO₃
5. CaCl₂

Give the formulate of the compounds formed from the following sets of elements:

1. Calcium and fluorine.
2. Hydrogen and sulphur.
3. Nitrogen and hydrogen.
4. Carbon and chlorine.
5. Sodium and oxygen.
6. Carbon and oxygen.

Write the formulae of the following compounds. Also name the elements present in them.

1. Water.
2. Ammonia.
3. Methane.
4. Sulphur dioxide.
5. Ethanol.

An element X forms the following compounds with hydrogen, carbon and oxygen:
H₂X, CX₂, XO₂, XO₃