Chemistry NCERT Exemplar Solutions Class 11th Chapter One

This is a Short Answer Type Questions as classified in NCERT Exemplar

(a) Is this statement true?  

Ans: Yes the given statement is true

(b) If yes, according to which law?

Ans: Multiple law of proportions: According to the Law of Multiple proportions, when two elements combine to generate more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of tiny whole numbers.

(c) Give one example related to this law

Ans:

C (g) + O (g) -> CO (g)

12 g    16 g       28 g

C (g) + O₂ (g) -> CO₂ (g)

12 g     32 g       44 g

This mass of Oxygen, which combines with a fixed mass of Carbon is in the simple ratio that is 16:32 or 1:2.

This is a Short Answer Type Questions as classified in NCERT Exemplar

If all gases are at the same temperature and pressure, Gay lussac's law of gaseous volumes states that gases combine or are created in a chemical reaction in a simple volume ratio.

H₂ (g) +          Cl₂ (g) →           2HCL (g)

1 volume      1 volume        2 volume

22.4 litre       22.4 litre        44.8 litre

2N₂ (g) +      O₂ (g) →            2N₂O (g)

2Vol             1Vol                  2Vol

45.4 litre     22.7 litre          45.4 litre

2: 1: 2

The above examples proved that gaseous volumes combine in a simple volume ratio.

This is a Short Answer Type Questions as classified in NCERT Exemplar

The number of moles of a substance (known as the solute) dissolved in precisely 1 litce of a solution is known as molarity (solvent and solute combined). As a result, the formula for estimating molarity is as follows:

Molarity = $\frac{\mathrm{n}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{s}\mathrm{}\mathrm{o}\mathrm{f}\mathrm{}\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{t}\mathrm{e}}{\mathrm{v}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{m}\mathrm{e}\mathrm{}\mathrm{i}\mathrm{n}\mathrm{}\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{}}$

The term molarity is also used to refer to molar concentration. As a result, molar concentration measurement is based on the volume of liquid in which a substance is dissolved. It's vital to remember that the volume is in litres, so if we have volume in mL we need to convert that in liters.

Molality is the number of moles of substance (also known as the solute) found in a given mass of solvent (in Kg ) in which it is dissolved.

 Molality is calculated by using the formula.

Major differences between Molarity and Molality are given as follows:

 1) Molarity is the concentration of a material determined as the number of moles of solute dissolved in poe litre of solution, whereas molality is the concentration calculated as the number of moles of solute found in one kilogram of solvent.

2) Molality is denoted by the symbol m, whereas molarity is denoted by the symbol M.

3) The molarity formula is moles per litre, but the molality formula is moles per kilogram.

4) Molarity is impacted by temperature changes, whereas molality is unaffected by temperature changes.

5) Changes in pressure affect molarity, but they do not affect molality.

6) Molarity can lead to an imprecise and inaccurate concentration, whereas molality can lead to an accurate and precise concentration measurement.