IGCSE Chemistry Paper-1: Specimen Questions with Answers 15 - 17 of 99
Question number: 15
Question
What is the relative molecular mass, Mr, of HNO3?
Choices
| Choice (4) | Response | |
|---|---|---|
a. | 63 | |
b. | 31 | |
c. | 5 | |
d. | 32 | |
Answer
a.Explanation
Relative molecular mass is the sum of all the relative atomic masses of the atoms in a molecule.
H = 1, N = 14, O = 16
Therefore
Question number: 16
Describe in Detail
The diagram shows how to obtain pure water from seawater. Where do water molecules lose energy?
Process of Getting Pure Water
Explanation
Here, Sea water contains .
- So, to obtain pure water ( ), there is a process called desalination is used to convert salt water into pure water.
Desalination Process:
- In this process, sea water is heated by any Bunsen flame as shown in figure above to convert sea water into gas state.
- Then this gas is condensed to make it liquid which is called distillation process which gives pure water.
Chemical Formula:
Question number: 17
Question
Element X forms an acidic, covalent oxide.
Which row shows how many electrons there could be in the outer shell of an atom of X?
Choices
| Choice (4) | Response | |
|---|---|---|
a. | 1 = N 2 = Y 6 = N 7 = Y | |
b. | 1 = N 2 = N 6 = Y 7 = Y | |
c. | 1 = Y 2 = Y 3 = N 6 = N 7 = N | |
d. | 1 = Y 2 = N 6 = Y 7 = N | |
Answer
b.Explanation
They must be 4,5, 6 or 7. For example element having 7 electrons on its outer shell such as Cl forms acidic oxide Cl207. Again element with 4 electrons on is outer shell like nitrogen forms NO2 an acidic oxide. Therefore it can have 6 or 7 electrons.