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Chapter 1 Basic Concepts Chemistry 11th Class Punjab Short Questions

Question No. 1 -

Answer No. 1 -

Question No. 2 - What is atomic mass unit? Give its values in grams.

Answer No. 2 - It is a unit of mass used for atoms and molecules and is equal to the 1/12 of the mass of an atom of carbon —12. It is obtained by dividing the unity by Avogadro's number (6.02 x 10^23).

Question No. 3 - How can the efficiency of a chemical reaction be expressed?

Answer No. 3 -

Question No. 4 - Define empirical formula and how it is related to molecular formula?

Answer No. 4 -

Question No. 5 - 180 grams of glucose and 342 grams of sucrose have same number of molecules, but different number of atoms present in them. Justify it.

Answer No. 5 -

Question No. 6 -

Answer No. 6 -

Question No. 7 - What is limiting reactant? How it helps to control the reaction?

Answer No. 7 - A limiting reactants is that one which is in lesser quantity and it is consumed earlier. Whenever, it is consumed then the further formation of the product stops, although the excess reagent is lying in the vessel. If the limiting reagent is not available to the excess quantity then product cannot be formed further.

Question No. 8 - N2 and CO have same number of electrons, protons and neutrons. Justify.

Answer No. 8 - No. of electrons in N2 = 7 + 7 = 14, number of protons in N2 = 7 + 7 = 14 and number of neutrons (14 - 7) = 7 + 7 = 14.

In CO, number of electrons in C = 6

Number of electrons in 0 = 8

Total number of electrons = 6 + 8 = 14

Number of neutrons in C = 6

Number of protons in 0 = 8

Total number of protons = 6 + 8 = 14

Question No. 9 - The atomic mass may be in fractions. Why?

Answer No. 9 - Most of the elements have isotopes. Isotopes have fractional atomic masses. The average of atomic masses of isotopes will be definitely in fractions. Moreover, the mono-isotopic elements have also fractional atomic, masses.

Question No. 10 - Define Solubility product and write down its application?

Answer No. 10 - Solubility product: The product of molar concentration of oppositely charged ions , in equilibrium with its solid salt in its saturated solution at a given temperature is called solubility product. Its is denoted by KSP
Application of KSp:
. Determination of KSP From solubility.
. Effect of common ion on solubility.

Question No. 11 - Distinguish between actual and theoretical yield.

Answer No. 11 -

Question No. 12 - Define Avogadro's number. How does it relate to the masses of chemical substances?

Answer No. 12 - It is the number of atoms, molecules or ions in one gram mole of an element, compound and ion. One gram mole of the substance is the atomic mass, molar mass or ionic mass taken in grams. It means that the number of the species is related with the masses of the species.

Question No. 13 -

Answer No. 13 -

Question No. 14 -

Answer No. 14 -

Question No. 15 - Molecular formula is multiple of empirical formula. Give an example.

Answer No. 15 - The empirical formula is the simplest whole number ratio of atoms of different elements present in a compound. Molecular formula tells us the actual number of atoms of each element in a molecule. Hence the empirical formula has to be multiplied with a suitable digit to get the molecular formula.

Question No. 16 - Why positively charged ions of isotopes are passed through magnetic field in the mass spectrometer?

Answer No. 16 - The positively charged ions bend perpendicular to the joining lines of the two poles, when passed through the magnetic field. In this way, magnetic field gives these ions semicircular path, scatters them on the basis of m/e values and compels them to fall on the electrometer. Electrometer develops the electric current. The strength of the torrent gives the relative of ions of definite m/v value.

Question No. 17 - What the experimental yield is mostly less than the theoretical yield?

Answer No. 17 - Experimental yield is mostly less than theoretical yield due to the following reasons.

(1) Mechanical loss of products due to:

(a) Filtration

(b) Separation by distillation

(c) Separating by separating funnel

(d) Washing

(e) Drying

(f) Crystallization

(2) Side reaction.

(3) Reversibility of reaction.

Chapter 1 Basic Concepts Chemistry 11th Class Punjab Short Questions

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