Elements

Q.

Write down the balanced chemical equation:

Hydrogen plus chlorine produces hydrogen chloride

Q. Bronze is an alloy made up of _______
and _______.

1. copper, zinc
2. copper, tin
3. zinc, tin
4. cobalt, tin

Q.

Write down the balanced chemical equation:

Carbon plus oxygen produces carbon dioxide

Q.

Write down the balanced chemical equation:

Aluminium plus chlorine produces aluminium chloride

Q.

Write down the balanced chemical equation:

Hydrogen plus nitrogen produces ammonia

Q.

What is the importance of chemical formula?

1. It shows the constituent elements

2. It represents the molecular mass of the compound

3. It represents the name of a compound

4. All of these

Q.

Identify the correct balanced equation from the following chemical reactions.

1. ${\text{2NaHCO}}_3\to \text{5}{Na}_2{\text{CO}}_3+{\text{CO}}_2+{\text{H}}_2\text{O}$

2. ${\text{CaC}}_2+{\text{H}}_2\text{O}\to {\text{C}}_2{\text{H}}_2+{\text{Ca(OH)}}_2$

3. $\text{2HgO}\to {\text{3Hg + 4O}}_2$

4. ${\text{2ClO}}_2+{\text{H}}_2\text{O}\to {\text{HClO}}_2+{\text{HClO}}_3$

Q. Oxygen is a/an ______ and carbon dioxide is a/an ________.

1. element, element
2. element, compound
3. compound, compound
4. compound, element

Q.

What happens when atoms combine to form a compound? Explain with an example.

Q.

The elements present in mercuric oxide are:

1. NaCl₂

2. KCl

3. NaCl₃

4. KCl₄

Q.

Write the complete symbol for the atom with the given atomic number $\left(\mathrm{Z}\right)$ and mass number $\left(\mathrm{A}\right)$.

(a) $\mathrm{Z}=17$, $\mathrm{A}=35$

Q.

State two reasons for not accepting the classification of elements on the basis of metals and non-metals.

Q.

Substance(s) written on the left-hand side of the chemical equation are known as

1. Reactant (s)

2. Product (s)

3. Reaction (s)

4. Both (a) and (b)

Q.

Write the balanced chemical equation for the following word equation

$\mathrm{Ammonia}+\mathrm{Oxygen}=\mathrm{Nitric}\mathrm{oxide}+\mathrm{Water}$

Q. Which of the following elements exist in liquid state at room temperature?

1. Hydrogen
2. Neon
3. Bromine
4. Silicon

Q. Identify the example of an element from the following options.

1. ${\text{H}}_2\text{S}$
2. ${\text{NH}}_3$
3. ${\text{CH}}_4$
4. ${\text{O}}_2$

Q.

In the table below, some of the elements of the periodic table with atomic numbers from 3 to 18 are given. These are represented by letters, which are not the usual symbols of the elements. [5 MARKS]

3	4	5	6	7	8	9	10
A						E	G
11	12	13	14	15	16	17	18
B	C		D			F

1. Which of these is a noble gas?

2. Which of these is a halogen?

3. Which of these is an alkali metal?

4. Which of these is an element with valency 4?

5. If A combines with F, what would be the formula of the resulting compound? What is the electronic arrangement of G?

Q.

What are non-metals? Name any four non-metals.

Q.

Solder is an alloy of lead and zinc.

1. True
2. False

Q. An element oxygen forms 2 oxides percentage of 1is 53.33 and formula is mo and in second oxide percentage is 69.56 then what is the formula

Q.

Metals compared to non-metals have wider variation of properties. Do you agree?

1. Yes

2. No

3. Changes from one element to next

4. Cannot be ascertained

Q.

Match the following elements with their atomic mass.

(i) Magnesium (ii) Carbon (iii) Oxygen (iv) Sulphur

(a) 32 (b) 16 (c) 12 (d) 24

1. (i) - (d), (ii) - (c), (iii) - (a), (iv) - (b)

2. (i) - (a), (ii) - (d), (iii) - (b), (iv) - (c)

3. (i) - (d), (ii) - (c), (iii) - (b), (iv) - (a)

4. (i) - (c), (ii) - (a), (iii) - (d), (iv) - (b)

Q.

Classify the following into elements and compounds:

Water, Hydrogen, Salt, Gold, Carbon dioxide, Iron

1. (i, iii, v) – A, (ii, iv, vi) - B

2. (i, iii, iv) – A, (ii, v, vi) - B

3. (i, ii, v) – A, (iii, iv, vi) - B

4. (i, ii, iii) – A, (iv, v, vi) - B

Q.

Define a pure substance. Name the types of pure substances you know.

Q. Name some elements that exist in:
1. Solid state
2. Liquid state
3. Gaseous state

Q.

Pick out the odd one from amongst the following which does not belong to the set:

Milk, honey, coal, brass, common salt.

Q.

The atomicity of $N{H}_3$ is _________.

1. four
2. seven
3. six
4. five

Q.

Mercury, water and bromine are elements.

1. True

2. False

Q.

Find the odd one out. Give a reason for your answer.

$\mathrm{Cu},\mathrm{Fe},\mathrm{He}\mathrm{and}{\mathrm{H}}_2$

Q.

Water is considered as a compound because:

1. it is made up of 3 molecules

2. it is made up of two elements

3. it has bonds present

4. it carries charge