5 marksh

Posted on May 1, 2019 in Chemistry

An aqueous solution of 2% non-volatile solute exerts a pressure of 1.004 bar at the normal boiling point of the solvent. What is the molar mass of the solute?

Answer

Here,

Vapour pressure of the solution at normal boiling point (p1) = 1.004 bar  (Given)

Vapour pressure of pure water at normal boiling point (p10) = 1.013 bar

Mass of solute, (w2) = 2 g

Mass of solvent (water), (w1) = 100 – 2 = 98 g

Molar mass of solvent (water), (M1) = 18 g mol – 1

According to Raoult’s law,

(p10 – p1) / p10    =  (w2 x M1 ) / (M2  x w1 )

(1.013 – 1.004) / 1.013 =  (2 x 18) / (M2 x 98 )

0.009 / 1.013  =   (2 x 18) / (M2 x 98 )

M2  =  (2 x 18 x 1.013) / (0.009 x 98)

M2  = 41.35 g mol – 1

Hence, the molar mass of the solute is 41.35 g mol – 1    What is the order of the reaction with respect to A and B?

Answer
Let the order of reactant A = x 
And the order of reactant B = y 
We have the formula



Take log both side we get 
log 2.821 = log 2 x
take the log of 2.821 and Use formula log ax = x log a we get 
0.4504 = x log 2 
Value of log 2 = 0.3020 
We get 
x = 0.4504/0.3020 = 1.5(approx) 
Answer 
The order of reactant A = 1.5
The order of reactant B = 0 

   manufature of suphuric acid: Introduction It was once said that a country’s wealth could be measured by its production of sulfuric acid (H2SO4). That may no longer be true, but the acid is still used in the manufacture of paints, fertilizers, plastics, fabrics, dyes, detergents, and many other useful products. In this unit you can find out how we make the acid in industry The Contact process The most important process for making sulfuric 

acid in industry is the Contact process. We can think of the Contact process as involving three stages. Look at the process shown in Fig.1 below: Stage 1Sulfur is imported from Poland or the USA. We can also obtain sulfur from the impurities in fossil fuels such as coal. In the first stage of the process, sulfur is burned in air to make sulfur dioxide gas:sulfur  +  oxygen  arrow.png  sulfur dioxide

S(l)  +  O2(g)  arrow.png  SO2(g) Stage 2 In the next stage, we convert the sulfur dioxide to sulfur trioxide: sulfur dioxide  +  oxygen  eqarrow.png  sulfur trioxide
2 SO2(g)  +  O2(g)  eqarrow.png  2 SO3(g)The reaction happens on a catalyst of vanadium(V) oxide to speed up the reaction. As much sulfur dioxide as possible is changed into sulfur trioxide, and releases of sulfur dioxide are prevented because it is a gas that causes acid rain.Stage 3 In the final stage, the sulfur trioxide is converted into sulfuric acid. The sulfur trioxide gas is absorbed into very concentrated sulfuric acid (a 98 per cent solution of H2SO4in water), producing a thick fuming liquid called oleum. The oleum is mixed carefully with water, and the sulfur trioxide in the oleum reacts with the water as follows: sulfur trioxide  +  water  arrow.png  sulfuric acid
SO3(g)  +  H2O(l)  arrow.png  H2SO4(l) You may wonder why the sulfur trioxide is not mixed directly with pure water. The problem is that this is a highly exothermic reaction, which would produce a fine mist of sulfuric acid that is difficult to condense and could escape to pollute the air.

*general charecterstic of group 17 The valence shell electronic configuration of these electrons is ns2np5. Thus, there are 7 electrons in the outermost shell of these elements.  The element misses out on the octet configuration by one electron. Thus, these elements look out to either lose one electron and form a covalent bond or gain one electron and form an ionic bond. Therefore, these are very reactive non-metals. Atomic Properties Let us now look at the various atomic properties of the group 17 elements. We will speak about the ionic and atomic radii, ionization enthalpy and more.

2) Ionisation Enthalpy These elements have higher ionization enthalpy. This value keeps on diminishing as we move down the group. This happens because of the increase in the size of the nucleus. However, it is interesting to note that fluorine has the highest ionization enthalpy than any other halogen, thanks to its minute size! 3) Electron Gain Enthalpy The electron gain enthalpy of these elements becomes less negative upon moving down the group. Fluorine has lesser enthalpy than chlorine. We can attribute it to the small size and the smaller 2p sub-shell of the atom of fluorine. 1) Oxidising Power All the halogens are great oxidizing agents. Of the list, fluorine is the most powerful oxidizing agent. It is capable of oxidizing all the halide particles to halogen. The oxidizing power reduces as we move down the group. The halide particles also act as reducing agents. However, their reducing capacity decreases down the group as well* @ Friedel–Crafts reactions The Friedel–Crafts reactions are a set of reactionsdeveloped by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring.[1] Friedel–Crafts reactions are of two main types: alkylation reactions and acylation reactions. Both proceed by electrophilic aromatic substitution@ Clemmensen reduction is a chemical reaction described as a reduction of ketones (or aldehydes) to alkanes using zincamalgam and concentrated hydrochloric acid.[1][2][3] This reaction is named after Erik Christian Clemmensen, a Danish chemist.The Clemmensen reduction@ Sandmeyer reaction The Sandmeyer reaction is a chemical reactionused to synthesize aryl halides from aryl diazonium salts using copper salts as reagents or catalysts. It is an example of a radical-nucleophilic aromatic substitution.