Question

ATOMS AND MOLECULES HOTS QUESTIONS:
Question 1:
(a) An element shows variable valencies 4 and 6. Write the formulae of its two oxides.
(b) An element forms an oxide A2O5.
(i) What is the valency of the element A ?
(ii) What will be the formula of the chloride of the element ?







Question 2:
(a) Why does not the atomic mass of an element represent the actual mass of its atom ?
(b) The atomic mass of an element is in fraction. What does it mean ?
(c) Why is the value of Avogadro’s number 6.022 x 1023 and not any other value ?
(d) Does one gram mole of a gas occupy 24.4 L under all conditions of temperature and pressure ?


Question 3:
A flask P contains 0.5 g mole of oxygen gas. Another flask Q contains 0.4 mole of ozone gas. Which of the two flasks contains greater number of oxygen atoms ?



Question 4:
What weight of calcium contains the same number of atoms as are present in 3.2 g of sulphur ?


Question 5:
Silicon forms a compound with chlorine in which 5.6 g of silicon is combined with 21.3 g of chlorine..
Calculate the formula of the compound (Atomic mass : Si = 28 : Cl = 35-5).

Question 6:
In magnesium sulphide, the ratio by mass of Mg and S is 3 : 4. What is the ratio of the number of Mg and S atoms ?​

Answer 1

Answer:

Explanation:

The chemical formula for the two oxides are:  

Explanation: In writing down the chemical formula for element X having valency 4 and 6 with oxide ion which has (-2) charge on it.

Element X having +4 oxidation state and oxide ion having -2 oxidation state.

This molecule requires 2 atoms of oxide for every 1 atom of X.

Hence, the chemical formula becomes  

Element X having +6 oxidation state and oxide ion having -2 oxidation state.

This molecule requires 3 atoms of oxide ion for every 1 atom of X.

Hence, the chemical formula becomes  

The formula for these two molecules are provided in the image attached.