Tag: metals, alloys and crystals

Questions Related to metals, alloys and crystals

An alloy is a specific type of substance that can best be described by which of the following?

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

  1. An alloy is a mixture of various metals that can also contain non-metal elements.

  2. An alloy is a compound made of different types of metals.

  3. An alloy can only contain metals from the transition elements.

  4. An alloy can only contain two pure metals mixed in even quantities.

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Correct Option: A
Explanation:

Ans : (A) An alloy is a mixture of various metals that can also contain non-metals elements.

Eg : Steel is an alloy of iron (metal) and carbon (non-metal).

Statement 1: A mixture of pure metals is called an alloy. The melting point of an alloy will be lower than either of the component metals
Statement 2: The new bonds are weaker.

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

  1. Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1

  2. Both the Statement 1 and Statement 2 are correct, but Statement 2 is not the correct explanation of Statement 1.

  3. Statement 1 is correct, but Statement 2 is not correct.

  4. Statement 1 is not correct, but Statement 2 is correct.

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Correct Option: A
Explanation:

Both statement right and statement $2$ are correct Explanation.

Note : [alloy is the mixture of different metals .each metal having different size and structural arrangements. The different sizes of atoms in an alloy make their arrangement less regular than a pure metal. This makes the bonds between the atoms weaker and lower melting point.

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.

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

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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.

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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

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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.

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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

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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. $\displaystyle Si$

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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

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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.