Tag: chemistry

Questions Related to chemistry

A bar of zinc generates a characteristic sound when bent, similar to_________.

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. Tin cry

  2. Water splashing

  3. Glass breaking

  4. None of above

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Correct Option: A
Explanation:

A bar of zinc generates a characteristic sound when bent, similar to tin cry. A tin cry is the characteristic sound heard when a bar of tin is bent. Variously described as a "screaming" or "crackling" sound, the effect is caused by the crystal twinning in the metal.

Platinum metal can be dissolved in:

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. hot conc. HCl

  2. hot conc. $HNO _3$

  3. hot dil. $H _2SO _4$

  4. a mixture of conc. HCl and $HNO _3$

Show answer
Correct Option: D
Explanation:
  • Traditional aqua regia is a mixture of concentrated nitric and hydrochloric acids in a ratio of 1:3 that can dissolve noble metals such as gold, platinum and palladium, even though the metals are not soluble in either acid alone.
  • Hence option D is correct answer.

The most reactive metal among the following is:

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. Fe

  2. Pt

  3. Ni

  4. Co

Show answer
Correct Option: A
Explanation:
The reactivity series is sometimes quoted in the strict reverse order of standard electrode potentials, when it is also known as the "electrochemical series":

$Li > Cs > Rb > K > Ba > Sr > Na > Ca > Mg > Be > Al > H( water) > Mn > Zn > Cr > Fe > Cd > Co$
$ > Ni > Sn > Pb > H(in acids) > Cu > Fe(+3) > Hg > Ag > Pd > Ir > Pt > Au $

So, according to this series, Iron is most reactive than $Pt, Ni, Co$

Arrange $Si, Be, Mg, Na$ and $P$ in the increasing order of metallic character:

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. $P<Be<Si<Mg<Na$

  2. $P<Si<Be<Mg<Na$

  3. $Si<P<Mg<Na<Be$

  4. $Na<Mg<Be<Si<P$

Show answer
Correct Option: B
Explanation:

metallic character increases down the group and decreases along the period as we move left to right. Hence the order of increasing metallic character is 

P to Na.

In vapour state a metal is mono atomic.

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. True

  2. False

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Correct Option: A
Explanation:

There are no definitive chemical bonds between two metal atoms in a lattice. They all are held together by the so-called metallic bond. The valence electrons are not shared between metal atoms. Hence they exist as a single metal atom in their lattice unit. 

However we need to apply so much energy to convert it into vapour . And when these change to vapour then no any electron is shared between any metal atom and stay in monoatomic.
When the energy is lowered these again form lattices.

Metals have:

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. high melting and boiling point

  2. low melting and boiling point

  3. high melting and low boiling point

  4. low melting and high boiling point

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Correct Option: A
Explanation:

1) High melting and boiling point

2) Metallic bonding is the strong attraction between closely packed positive metal ions and a 'sea' of delocalised electrons.

3) The attraction between the metal ions and the delocalised electrons must be overcome to melt or to boil a metal.

4) These attractive forces are strong, so metals have high melting and boiling points.

Sodium and potassium  are soft even after being metals because of:

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. strong intermolecular forces

  2. weak cohesive forces

  3. high melting point

  4. low boiling point

Show answer
Correct Option: B
Explanation:

Hardness of a metal is determined by the strong cohesive forces between the atoms. The cohesive forces between atoms of these metals are very weak. The bonding in these metals is weak and electrons are not located over a single atom but over a number of atoms. The weak bonding results in softness of metal.

A metal which is lighter than water is:

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. lithium

  2. gold

  3. silver

  4. iron

Show answer
Correct Option: A
Explanation:
Lithium has a density of (0.534 g/cm3) which is lower than water (1 g/cm$^3$). Two other metallic elements are less dense than water. Potassium has a density of 0.862 g/cm$^3$ while sodium has a density of 0.971 g/cm$^3$. All of the other metals on the periodic table are denser than water. While lithium, potassium, and sodium are all light enough to float on water, they are also highly reactive.

Metals generally extracted by electrolysis of their fused salts are highly:

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. electropositive 

  2. electronegative

  3. depends on temperature

  4. depends on impurities in the metal

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Correct Option: A

You may be "shocked" to discover that metals are good conductors of electricity. Which of the following statements best explains why metals behave in this way?

chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

  1. Metallic bonding can be described as an "electron sea" with mobile valence electrons.

  2. Metals tend to have higher densities than nonmetals.

  3. Metals tend to have higher melting points than nonmetals.

  4. Metals tend to have rather large values for electronegativity.

Show answer
Correct Option: A
Explanation:

Ans : (A) Metallic bonding can be described as an 'Electron Sea' with mobile valence Electron.

Note: - In metals, the outer Electrons of atom belong to a 'cloud' of delocalised $e^{\ominus}$. They are no longer firmly held by a specific atom, but instead they can move freely through the lattice of positive metals ions. $\therefore$ Metals are good conductor of Electricity.