Tag: chemistry

Questions Related to chemistry

John Newlands arranged the known elements in a/an  ______ order of their atomic _______ .

chemistry the periodic table newland's law of octaves development of the modern periodic table into the history

  1. increasing, masses

  2. decreasing, masses

  3. increasing, numbers

  4. decreasing, numbers

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Correct Option: A
Explanation:

John Newlands arranged the known elements in an increasing order of their atomic masses. He started with the element having the lowest atomic mass ( hydrogen ) and ended at thorium which was the $56^{th}$ element. Some of the elements satisfying this order are arranged as $H, Li, Be, B, C, N, O$.

The given arranged sequence on the basis of their increasing atomic masses represents which law of classification of elements?  

$F, Na, Mg, Al, Si, P, S, Cl$ & $K$
chemistry the periodic table newland's law of octaves development of the modern periodic table into the history

  1. Modern table

  2. Newton's law

  3. Newland's law of octaves

  4. Mendeleev's periodic table

Show answer
Correct Option: C
Explanation:

Elements have been arranged in the following sequence on the basis of their increasing atomic masses.

    $F, Na, Mg, Al, Si, P, S, Cl$ & $K$

Law of octaves is given by the English chemist J.A.R. Newlands in 1865.
It states that if chemical elements are arranged according to increasing atomic weight, similar physical and chemical properties occur after each interval of seven elements.

Newlands was the first to detect a periodic pattern in the properties of the elements and anticipated later developments of the periodic law.

For which of the pair Newland octave rule is not applicable?

chemistry the periodic table newland's law of octaves development of the modern periodic table into the history

  1. $Li,\ Na$

  2. $C,\ Si$

  3. $Mg,\ Ca$

  4. $Cl,\ Br$

Show answer
Correct Option: D
Explanation:

According to Newland Octave law, when elements are arranged in increasing atomic mass every eighth element has similar properties to the first element.

Further the law was not applicable to elements of higher atomic masses. So, law was applicable till calcium.
Hence, $Cl,Br$ is not applicable to Newland Octave Rule.

Who presented the law of octave? 

chemistry the periodic table newland's law of octaves development of the modern periodic table into the history

  1. Dobereiner

  2. Newland

  3. Lother Meyer

  4. Mendeleev

Show answer
Correct Option: B
Explanation:
According to Newland's law of octaves, when elements are arranged by increasing atomic mass, the properties of every eighth element starting from any element are a repetition of the properties of the starting element.
Option B is correct.

Which of the following statement is incorrect about electrochemical cell?

electrical cells patterns and properties of metals chemistry

  1. Electrons are released at anode

  2. Chemical energy is converted into electrical energy

  3. Salt bridge maintains the electrical neutrality of the electrilytes

  4. Cell can work indefinitely

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Correct Option: C

The following electrochemical cell is taken $Cu| Cu^{2+}(aq)|| Ag^{+}(aq))| Ag$ and has emf $E _{r}>0$ by which of the following actions $E _{1}$ increases?

electrical cells patterns and properties of metals chemistry

  1. Adding $NH _{3}$ to the cathodic chamber

  2. Adding $HCl$ to the cathodic chamber

  3. Adding $AgNO _{3}$ to the anodic chamber

  4. Adding $NH _{3}$ to the anodic chamber

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Correct Option: A

Find out ${E} _{cell}$ of following electrochemical cell (${E} _{{Br} _{2}/{Br}^{-}}=1.09V$)
$Pt(s)\mid {Br} _{2}(l)\mid{Br}^{-}(0.01M)\mid\mid{H}^{+}(0.01M)\mid{H} _{2}(g)(1bar)\mid Pt(s)$

electrical cells patterns and properties of metals chemistry

  1. $-1.32V$

  2. $+1.09V$

  3. $-2.15V$

  4. $-1.92V$

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Correct Option: C

The following electrochemical cell has been set up: $Pt(s)|Fe^{3+}, Fe^{2+}(a=1)||Ce^{4+}, Ce^{3+}(a=1)|Pt(s); E^{\circ}(Fe^{3+}|Fe^{2+})= 0.77V$; $E^{\circ}(Ce^{4+}|Ce^{3+})= 1.61V$. If an ammeter is connected between the two platinum electrodes, predict the direction of flow of current. Will the current increase or decrease with time?

electrical cells patterns and properties of metals chemistry

  1. Ce electrode to Fe electrode, decrease

  2. Ce electrode to Fe electrode, increase

  3. Fe electrode to Ce electrode, decrease

  4. Fe electrode to Ce electrode, increase

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Correct Option: A

After some time, the voltage of an electrochemical cell becomes zero. This is because ____________________.

electrical cells patterns and properties of metals chemistry

  1. their electrode potential becomes zero.

  2. their reduction potential become equal but have opposite sign

  3. their reduction potential become equal and have the same sign.

  4. the ions of the electrolyte in the salt bridge stop moving.

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Correct Option: B

Which one of the following statements is incorrect regarding an electrochemical cell?

electrical cells patterns and properties of metals chemistry

  1. The electrode on which oxidation takes place is called anode.

  2. Anode is the negative pole.

  3. The direction of the current is same as that of the direction of flow of electrons.

  4. The flow of current is partly due to flow of electrons and partly due to flow of ions.

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Correct Option: C