IGCSE Chemistry Paper-1: Specimen Questions with Answers 85 - 86 of 99
Question 85
Question
MCQ▾Which statement is true about a chemical reaction:
- It is exchange of atoms where the atoms disappear to form products.
- It is the exchange of atoms where new bonds are formed in the products
- It is exchange of atoms where the atoms does not disappear to form products.
Choices
| Choice (4) | |
|---|---|
a. | 1) and 3) |
b. | 2) and 3) |
c. | Only 3) |
d. | All of the above |
Answer
b.Explanation
The chemical reactions are simply the exchange of atoms in the reactants to form products. Neither the atoms disappear in reaction nor new atoms appear in the same. In chemical reactions bonds present in reactants break and new bonds are formed. This all depends on the nature of reaction.
Question 86
Question
MCQ▾A metal X when treated with sodium hydroxide produces a gas. The same gas is produced when X is treated with hydrochloric acid. When a match stick is brought near the gas a pop sound is produced. What could the gas be?
Choices
| Choice (4) | |
|---|---|
a. | Oxygen |
b. | Nitrogen |
c. | Hydrogen |
d. | Carbon di oxide |
Answer
c.Explanation
The chemical equations for the following reactions would be:
Also, Hydrogen gas is highly flammable. It forms explosive mixtures with air. The reaction of H2 gas with atmospheric oxygen is explosively fast. The pop sound you hear is a mini-shock wave. If the H2 is collected in a balloon, about 10 - 15 cm. in diameter, the “pop” becomes a very loud “bang”.