Question

Chemistry (27 Marks)

Q1: In water the proportion of Hydrogen and oxygen by mass is ………… (1)

Q2: What is law of constant proportion? (1)

Q3: What we call those particles which have more electrons than normal atom?

(1)

Q4: Write down the formula of calcium oxide. (1)

Q5: What is the mass of 0.2 mole of oxygen atoms? (1)

Q6: What is the numerical value of Avogadro number? (1)

Q7: What are divalent ions? (1)

Q8: Write the name of a particle which contain 10 electrons, 11 protons and 12

neutrons? (1)

Q9: Calculate the formula mass of following compound. (3)

a) Sodium oxide

b) Aluminium oxide

Q10: Write the formula of following compound. Also write the element present in

it. (3)

a) Water

b) Ammonia

c) Methane

Q11: An element X has a valencyof 2 .write the simplest formula for: (3)

a) Bromide of the element

b) Oxide of the eleement

Q12: Explain the formation of: (5)

1) Sodium ion

2) Chloride ion​

Answer 1

Answer:

copper sulphate CUSO4

Answer 2

1 .

ANS - 8:1

2 .

ANS - Law of constant proportion states that a chemical compound always contains exactly the same proportion of elements by mass. For a given unique chemical compound, its elemental composition is same for any sample that exists.

3 .

ANS - Having more electron is known as anion and having less electron is called cation.

4 .

ANS - The chemical formula of calcium oxide is CaO. The molecule is formed by the calcium cation Ca

+2

and the oxygen anion O

−2

, which form an ionic bond

5.

ANS - What is the mass of : (a) 0.2 mole of oxygen atoms? (b) 0.5 mole of water molecules? Ans. ∴ 0.2 mole of oxygen atoms = 16 × 0.2 = 3.2 g

6.

ANS - Avogadro's number, number of units in one mole of any substance (defined as its molecular weight in grams), equal to 6.02214076 × 1023. The units may be electrons, atoms, ions, or molecules, depending on the nature of the substance and the character of the reaction (if any). See alsoAvogadro's law.

7.

ANS - A divalent cation is an cation with valence of 2+. This type of ion may form two chemical bonds with anions. Also Known As: bivalent cation.

8.

ANS - Sodium has an atomic number of 11. The number of protons determines the atomic number.