Science Olympiad Test: Metals and Non-Metals- 2 - Free MCQ with solutions

An amphoteric oxide is an oxide that can act either as an acid or as a base to create salt and water in a reaction. The oxidation states open to a chemical species are based on amphoterism. Amphoteric oxides and hydroxides are formed when metals have several oxidation states.
The reactions are given below:
Acts as a basic oxide
Al₂O₃+ 6HCl → 2AlCl₃ + 3H₂O
Acts as an acidic oxide
Al₂O₃+ 2NaOH → 2NaAlO₂ + H₂O

Because X loses electrons, it is an electropositive metal, whereas Y gains electrons, making it a non-metal.

• An ionic compound is a mixture of metals and nonmetals.
• Ionic compounds are solids with a high melting point and good conductivity in molten form.

Magnesium reacts with cold water to form magnesium oxide and evolves hydrogen gas is a wrong statement because Magnesium Hydroxide is formed not Magnesium oxide.

Iron is more reactive than copper hence it displaces copper in the reaction to form FeSO_4.

• Iron displaces copper from its solution. Therefore, copper is less reactive than iron.
• Copper does not displace any metal therefore it is the least reactive.

Given:
Test tube A contains concentrated HCl
Test tube B contains concentrated HNO₃
Test tube C contains a mixture of concentrated HCl and HNO₃ in 3 : 1 ratio, called aqua regia.

Observations:
No reaction in A and B → the metal does not react with HCl or HNO₃ alone
Metal dissolves in C → the metal reacts with aqua regia

Important facts:
Gold (Au) does not react with HCl or HNO₃ individually
Gold dissolves in aqua regia
Aluminium (Al) reacts with HCl
Copper(Cu) reacts with HNO₃
Silver (Ag) reacts with HNO₃

Since the metal reacts only with aqua regia and not with individual acids, the metal must be gold.

Correct Answer: Au

Metals are usually reactive. Pure copper metal when left exposed to air starts reacting with some gases in the air like carbon dioxide and water vapor. This leads to the formation of copper carbonate and others.
Copper carbonate makes the shiny copper metal become dull and greenish in color.

Silver article become black when exposed to air, because of presence of H₂S gas present in air. Thus, silver on reaction with H₂S forms a black coating of Ag₂S.
Ag (Silver) + H₂O (Hydrogen sulphide) → Ag₂S (Silver sulphide) + H₂

Metals that exist in their native state are found in nature in their pure, uncombined form because they are very unreactive. Gold (Au) and silver (Ag) are both very low in the reactivity series and are commonly found in their native state. Copper (Cu) can sometimes be found in its native state, but much less commonly than gold and silver. Zinc (Zn) is a reactive metal and is never found in its native state. Therefore, the correct answer is (ii) Au and (iv) Ag.

X = 2, 8 = 10: It is the electronic configuration of neon.
Y = 2, 8, 7 = 17: It is the configuration of the halogen family of chlorine atom which is non-metal
Z = 2, 8, 2 = 12: It is the configuration of alkaline earth metals of magnesium atom which is metal.
Therefore, X is a noble gas, Y is a non-metal, and Z is a metal.

All metals are solids at room temperature is not correct. The following points clarify this:

• Mercury is the only metal that is liquid at room temperature.
• Most metals, like iron and copper, are indeed solids.
• Exceptions exist; for instance, gallium and cesium can melt at low temperatures.

Thus, the statement that all metals are solids is inaccurate due to these exceptions.

Carbon tetrachloride is a covalent compound and dissolves in ether and alcohol like organic compounds. Hydrochloric acid is the gas dissolved in water while hydrogen chloride is the gaseous compound which is covalent in nature by its molecular structure. NaCl and KCl are ionic compounds which dissociate into its ions in the aqueous solution.

Electromagnetic separation is used to concentrate magnetic ores. From the following options, only cuprite is non-magnetic in nature so it cannot be concentrated by electromagnetic separation technique.

HON₃ is oxidising agent. It oxidzes metal to metal oxide which further dissolves in HNO₃ to form metal nitrate and HNO₃ itself is reduced to NO₂ or NO or N₂O depending upon the nature of the metal and concentration of acid. Mn and Mg are the only metals which react with dilute of HNO₃ to produce H₂ gas.

• An ore consists of desired metal compound from which the metal can be extracted profitably.
• Cinnabar is an ore of mercury. Its chemical formula is HgS.
• It is the most common source used for refining elemental mercury.

Ores are minerals from which metals can be extracted conveniently and profitably. Let us take the ore of aluminium, that is bauxite.
Minerals are substances from which metals cannot be extracted conveniently and profitably. For example, Kaolinite is a clay mineral of aluminium. But it is not an ore because aluminium cannot be extracted profitably.
Hence, we can conclude that all ores are minerals but all minerals are not ores.