Tag: chemistry

Questions Related to chemistry

Surface chemists design alloys for specific functions in everyday life.
Which of the following does not demonstrate a benefit of using an alloy?

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. Gold is mixed with copper or silver to make a less expensive form that can be used in jewelry.

  2. Smaller atoms of one metal are incorporated into the structure of larger metal atoms to reduce malleability and improve strength of the structure.

  3. Densities of metals are closely matched to increase desirable properties without increased cost.

  4. The conductivity has been eliminated due to the stronger bonding of the different types of metals.

Show answer
Correct Option: B
Explanation:

Ans: (B) Smaller atoms of one metal are incorporated into the structure of large metal atom to redue malleability and improve strength of structure.

Note : - Smaller atoms have greater ratios of surface area to volume which means greater ratio of atom boundary to dislocation.

Which substance would have the lowest melting point?

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. ${ Mg } _{ 3 }{ Al } _{ 2 }$

  2. $Ca{ Cl } _{ 2 }$

  3. ${ Cu } _{ 2 }Sn$

  4. ${ C } _{ 12 }{ H } _{ 22 }{ O } _{ 11 }$

Show answer
Correct Option: D
Explanation:

$C _{12}H _{22}O _{11} (Sucrose) -180^{\circ}C$

$Mg _{3}Al _{2}, CaCl _{2}$ and $Cu _{2}S _{n}$ show ionic bonding where as $C _{12}H _{22}O _{11}$ show covalent bonding. And we know melting point of covalent bonded compound is less then ionic compound.

Which of the following choices provides the BEST explanation for the fact that bronze, an alloy of copper and tin, is a good conductor of electricity?

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. Copper and tin have similar atomic radii.

  2. Copper and tin have similar melting points.

  3. The structure contains a "sea" of mobile valence electrons.

  4. The structure consists of strong covalent bonds between the atoms.

Show answer
Correct Option: C
Explanation:
Both tin and copper alloys having a free electron in their outermost valence shell. When potential energy is provided these electron move from one end to another and conduct the electricity.

An alloy of any metal with mercury is called amalgam and the electrical conductivity of an alloy is more than that of pure metals.

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Alloys of mercury with metals like silver, copper, tin, zinc are used as amalgams.

Steel, composed of carbon and iron, is an example of an interstitial alloy.
Which of the following choices represents the best explanation for the fact that steel is harder and stronger than pure iron?

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. Carbon atoms are more reactive with oxygen than iron atoms. This prevents the steel from forming rust.

  2. Carbon atoms are smaller than iron atoms. Carbon atoms fill the spaces between iron atoms, making the structure more rigid.

  3. Carbon atoms form strong bonds with other carbon atoms. This forms a protective layer on the surface of steel.

  4. Both carbon and iron are good conductors of electricity. This makes steel harder and stronger than pure iron.

Show answer
Correct Option: B
Explanation:
Ans : (B) Carbon atoms are smaller than iron atoms. Carbon atoms fill the spaces between iron atom, making the structure $\%$ more rigid.
Note : - Steel is interstitial alloy of iron and carbon, due to smaller size of carbon, it easily fit between the metal atoms (iron) and provide Extra bonding to neighbouring atom, which makes alloy harder stronger (rigid).

When items of jewellery made of base metals like copper, iron or nickel are placed in a solution containing a compound of gold, a film of gold is deposited by:

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. cooling to $5$ degree centigrade

  2. adding acid

  3. heating

  4. passing an electric current

Show answer
Correct Option: D
Explanation:

Electroplating is the process in which a layer of a metal is deposited on metallic or non-metallic electrode by electrolysis in an electrolytic cell.

When items of jewellery made of base metals like copper, iron or nickel are placed in a solution containing a compound of gold, a film of gold is deposited by the process of electroplating which  requires passing an electric current in it.
Hence option D gives the correct answer.

Which of the following shows both the properties of both metals and non-metals?

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. $\displaystyle F$

  2. $\displaystyle Li$

  3. $\displaystyle Fe$

  4. $\displaystyle He$

  5. $\displaystyle Si$

Show answer
Correct Option: E
Explanation:

Silicon is a metalloid, a semimetallic element that is neither a metal nor a nonmetal but has some of the properties or characteristics of the two. A semi-metal in the periodic table, silicon is one of the elements that can't be found in nature in its elemental form. It is also one of the most common elements in nature, accounting for about 28 percent of the earth's crust by mass.

Monel metal is a metallic alloy of copper and nickel with $5$% iron. It is used in making:

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. locks

  2. strong boxes

  3. almirahs

  4. motor parts

Show answer
Correct Option: A
Explanation:

Monel is a group of nickel alloys, primarily composed of nickel (up to 67%) and copper, with small amounts of iron, manganese, carbon, and silicon. Stronger than pure nickel, Monel alloys are resistant to corrosion by many agents, including rapidly flowing seawater.

Being stronger than pure nickle Monel metal is used in making locks.
Hence option A is correct answer.

Which of the following is not an alloy containing tin metal?

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. Solder for soldering electrical contacts

  2. Pewter for hardness

  3. Bronze for statues

  4. Brass for articles like bangles and utensils

Show answer
Correct Option: D
Explanation:

 Brass for articles like bangles and utensils.

Brass is an alloy of copper and zinc having molecular formula ${Cu} _{3}{Zn} _{2}$

Which of the following is a steel that is resistant to acids?

chemistry elements and compounds alloys and their properties metals, alloys and crystals chemical bonding and structure

  1. Nickel alloy steel

  2. Molybdenum steel

  3. Stainless steel

  4. Cobalt alloy steel

Show answer
Correct Option: B
Explanation:

Molybdenum can be obtained from the minerals molybdenite, wulfenite and powellite. It is also obtained as a byproduct during tungsten and copper mining and processing. It has one of the highest melting points of all pure elements; however it is not resistant to acids.Hence, molybdenum steel is also not resistant to acids.

Hence option B is correct answer.