IGCSE Chemistry Paper-1: Specimen Questions with Answers 15 - 17 of 99
Question 15
Question
MCQ▾What is the relative molecular mass, Mr, of HNO3?
Choices
Choice (4) | |
---|---|
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 16
Describe in Detail
Essay▾The diagram shows how to obtain pure water from seawater. Where do water molecules lose energy?
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 upper figure 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 17
Question
MCQ▾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) | |
---|---|
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.