Question

E. Answer the following questions.
1.
Write the steps involved in writing the chemical formula of calcium phosphate.
2.
How is a chemical change different from a physical change?
3.
Neutralisation reaction is a chemical change. Justify this statement with the
help of an example.
4. Define a decomposition reaction and give an example of the same.
5. Classify the following reactions into different types, giving reason.
(a) CaO(s) + SiO,(g)
CaSiO,(s)
(b) KOH(aq) + HCl(aq)
KCl(aq) + H,O(1)
(c) Cu(s) + 2AgNO,(aq)
-Cu(NO),(aq) + 2Ag(s)
heat
(d) BaCO,(s)
- Bao(s) + CO,(g)​

Answer 1

Answer:

Calcium :

Chemical formula of calcium = Ca

Valence of calcium = 2

Phosphate :

Chemical formula of phosphate = PO₄

Valence of phosphate = 3  

We need to write the chemical formula of calcium phosphate  

Using interching valency formula:

Calcium phosphate= $Ca_{3}(PO_{4})_{2}$

Therefore, The chemical formula of calcium phosphate is $Ca_{3}(PO_{4})_{2}$

2. A chemical change affects the composition of a substance and a chemical change only affects the physical properties of a substance like shape, size, smell, colour etc.

3. Neutralization reaction is a chemical change it involves the reaction of base and an acid who gives two new compounds, water and salt. For eg. Hcl+Naoh----> Nacl+ H2O. In neutralization reaction the acid and base reacts to form salt and water so there is chemical change that is new compounds are form .

4. A decomposition reaction occurs when one reactant breaks down into two or more products. Example: the breakdown of hydrogen peroxide to water and oxygen.

5. a. Combustion reaction because two substances combine together to form a new substance.

b. Neutralization reaction because an acid and a base react together to form salt and water

c. Displacement reaction because Cu displaces Ag (silver) from $AgNo_{3}$ solution.

d. Decomposition reaction because one substance breaks to form two substances.