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Multiple choice chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

In Poling process, Hydrocarbon gases escaping from the poles act as _____ agents.

  1. reducing

  2. oxidation

  3. both

  4. none
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Poling is a process in which the impure metal containing oxide as impurities is purified. It is melted and stirred with green poles of wood. Hydrocarbon gases escaping from the poles act as reducing agents and reduce the oxide impurities e.g., impurity of Cu$ _2$O which is reduced to metallic copper by poling.
$Cu _2O + CO \rightarrow 2Cu + CO _2 \uparrow$
$Cu _2O + H _2 \rightarrow 2Cu + H _2O$

Multiple choice chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

In polling, wood gas is responsible for the removal of volatile impurities.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

True. Polling is used for converting Copper Oxide $(Cu _2O)$ to Copper $(Cu)$. When ore is heated with wood poles, the poles release charcoal, shoot and gas. The gas released reduces $CuO$ to $Cu$. So the gas takes away impurities. 

Multiple choice chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

Which of the following methods is used to remove lead present in silver ?

  1. Cupellation

  2. Distillation

  3. Poling

  4. Lavigation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Cupellation is a process of separation of gold or silver from impurities by melting the impure metal in a cupel (a flat porous dish made of refractory or high-temperature resistant material  ) and then directing a blast of hot air on it in a special furnace. The impurities, including lead,copper, tin, and other unwanted metals, are oxidized and partly vaporized and partly absorbed into the pores of the cupel.

Multiple choice chemistry principles and processes of isolation of elements refining of metals basics of metallurgy basic metallurgical processes

Poling process:

  1. reduces $SnO _2$ to Sn

  2. oxidizes impurities like iron and removes as scum

  3. uses green poles

  4. uses brown poles
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

Poling: A refining process of crude metal for removing metal oxide impurities by stirring molten metal in a ladle with a pole of green wood (poles).


In the poling process, the reduction of oxides to metal atom will be done.

Ex: Extraction of copper from copper oxide and Sn from $SnO _2$.

Hence options A,B & C are correct.

Multiple choice chemistry the periodic table mendeleef's periodic table mendeleev's periodic law and its limitations mendeleev's periodic table development of the modern periodic table into the history

The first periodic law stated by Mendeleev was :

  1. there is no correlation in the properties and atomic weights of the elements

  2. the properties of the elements are a periodic function of their atomic numbers

  3. the properties of the elements are a periodic function of their atomic weights

  4. the properties of the elements are a periodic function of their empirical formula
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The first periodic law stated by Mendeleev was, "the physical and chemical properties of the elements are a periodic function of their atomic weights (atomic masses)." The elements having similar properties appeared in the same group (vertical column).
Multiple choice chemistry the periodic table mendeleef's periodic table mendeleev's periodic law and its limitations mendeleev's periodic table development of the modern periodic table into the history

A certain gas takes three times as long to effuse out as helium. Its molecular mass will be :

  1. 27u

  2. 36u

  3. 64u

  4. 9u
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Some gases are taking three times as long to effuse out as helium.

The rate of effusion is always inversely proportional to the square root molecular mass.

The rate of effusion is the ratio of the volume effused to the time taken as follows.

$ \dfrac{{V} _{1}}{{t} _{1}} \times \dfrac {{t} _{2}}{{V} _{2}}$  $=\sqrt {\dfrac{{M} _{{w} _{2}}}{{M} _{{w} _{1}}}}$

 Volume is same, so

$\dfrac{3}{1}= \sqrt{\dfrac{{M _{w2}}}{4}}$

So, $M _{w2} =  36\ unit.$

The molecular mass of the gas is 36 u.

So, the correct option is A.

Multiple choice chemistry the periodic table mendeleef's periodic table mendeleev's periodic law and its limitations mendeleev's periodic table development of the modern periodic table into the history

Which of the following is not a merit of Mendeleev's periodic table?

  1. It helped in correcting the atomic masses of some of the elements

  2. He predicted the properties of some undiscovered elements and left gaps for them

  3. He framed the periodic table with vertical and horizontal columns and gave shape to it

  4. He gave separate places to isotopes in his periodic table
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Merits of Mendeleev's periodic table:
1) It helped in correcting the atomic masses of some of the elements e.g. beryllium was corrected from 13.5 to 9. Similarly, indium, gold, platinum etc.
2) He predicted the properties of some undiscovered elements and left gaps for them e.g. Eka-boron, eka-aluminum and eka-silicon names were given for scandium, gallium, and germanium (not discovered at the time of Mendeleev).
3) He framed the periodic table with vertical and horizontal columns and gave shape to it.
4) Isotopes are the atoms of the same element having different atomic masses. Therefore, according to Mendeleev’s classification, these should be placed at different places depending upon their atomic masses. For example, hydrogen isotopes with atomic masses 1,2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table because of their similar properties.
Hence, option $D$ is correct.
Multiple choice chemistry the periodic table mendeleef's periodic table mendeleev's periodic law and its limitations mendeleev's periodic table development of the modern periodic table into the history

Numbering of groups as 1, 2, ........... 18 was adopted by IUPAC in :

  1. 1986

  2. 1906

  3. 1908

  4. 1988
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Two earlier group number systems exist: CAS (Chemical Abstracts Service) and old IUPAC. Both use numerals (Arabic or Roman) and letters A and B. In 1988 the new system simply numbers the groups increasingly from left to right on the standard periodic table. 

Multiple choice chemistry the periodic table mendeleef's periodic table mendeleev's periodic law and its limitations mendeleev's periodic table development of the modern periodic table into the history

Nobel gases were included in Mendeleev's periodic table in the: 

  1. 1st group

  2. 7th group

  3. 8th group

  4. none of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Mendeleevs Periodic Table:
Elements are arranged in the periodic table in the increasing order of their relative atomic masses.
Mendeleev divided his periodic table in eight groups and seven periods.
Groups from I to VII are meant for normal elements and group VIII is for transition elements.
Groups from I to VII have been divided in two sub groups, while group VIII is meant for three elements.
Periods from 4th to 7th have been divided in two series: 1st series and 2nd series.
Elements having similar properties have been kept in the same group. For example; lithium, potassium, rubidium, etc. are in 1st group.

Multiple choice chemistry the periodic table mendeleef's periodic table mendeleev's periodic law and its limitations mendeleev's periodic table development of the modern periodic table into the history

Whose name is associated with the development of periodic table ?

  1. Newlands

  2. Mendeleev

  3. Dalton

  4. Doberiener
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mendeleeve is credited with the development of his periodic table to illustrate periodic trends of known elements and predicted properties of unknown elements also.