Tag: chemistry

Questions Related to chemistry

Hydrogen is not obtained when Zn reacts with:

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. cold water

  2. hot NaOH solution

  3. dil. H$ _2$SO$ _4$

  4. dil. HCl

Show answer
Correct Option: A
Explanation:

Zinc is a moderately reactive metal that does not react with cold water and hence no gas is evolved.

$Zn+H _2O \rightarrow $ No reaction.

When a small piece of dry sodium is put in water, it reacts vigorously to produce:

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. nitrogen gas

  2. hydrogen gas

  3. carbon dioxide gas

  4. sulphur dioxide

Show answer
Correct Option: B
Explanation:
Most of the metals do not react with water. However,alkali metals react vigorously with water. Reaction of sodium metal with water: Sodium metal forms sodium hydroxide and liberates hydrogen gas along with lot of heat when reacts with water.
 When sodium reacts with water, sodium hydroxide is formed hydrogen gas as a byproduct that gets burnt with a bright flame making the reaction highly exothermic.
  

The incorrect statement among the following for magnesium metal is:

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. it burns in oxygen with dazzling white flame

  2. tt reacts with cold water to form magnesium oxide and evolves hydrogen gas

  3. it reacts with hot water to form magnesium hydroxide and evolves hydrogen gas

  4. it reacts with steams to form magnesium hydroxide and evolves hydrogen gas

Show answer
Correct Option: D
Explanation:

Magnesium burns in steam to produce white magnesium oxide and hydrogen gas. If a metal reacts with cold water the metal hydroxide is formed but if it reacts with steam the metal oxide is formed.

$2Fe(s) + 3H _2O(g)\rightarrow$

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. $Fe _2O(s) + 3H _2(g)$

  2. $Fe _2O _3(s) + 3H _2(g)$

  3. $Fe _2O _3(s) + 3H _2O(g)$

  4. None of above

Show answer
Correct Option: B
Explanation:

Iron is less reactive than sodium, potassium, calcium, zinc and magnesium. It does not react with cold and hot water, but it reacts with steam to form magnetic oxides.
$ 2Fe(s) + 3H _2O(g) \rightarrow Fe _2O _3(s) + 3H _2(g) $

In case of reaction between sodium and cold water, hydrogen burns with _______ flame, whereas, in case of reaction between potassium and cold water, hydrogen burns with _____ color.

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. Yellow, lilac

  2. Orange, yellow

  3. Orange, lilac

  4. Lilac, yellow

Show answer
Correct Option: C
Explanation:

When sodium is added to water, the sodium melts to form a ball that moves around on the surface. It fizzes rapidly, and the hydrogen produced may burn with an orange flame before the sodium disappears.When potassium is added to water, the metal melts and floats. The hydrogen ignites instantly. The metal is also set on fire, with sparks and a lilac flame. 

The reaction of sodium metal with cold water is

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. Endothermic

  2. Exothermic

  3. Both a and b

  4. Neither a nor b

Show answer
Correct Option: B
Explanation:

Metals like sodium and potassium react violently with cold water. These reactions are exothermic. The reaction is so violent and exothermic that the hydrogen which is evolved immediately catches fire.

What will be the colour of the blue cobalt chloride paper dipped in water?

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. Yellow

  2. Blue

  3. Pink

  4. Green

Show answer
Correct Option: C
Explanation:

Cobalt chloride paper is used to test for the presence of water. In this test, the colour of paper changes from blue to pink.


Hence the correct option is C.

Which of the following exists as cations with delocalized electrons?

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. Non-polar covalent substance

  2. Polar covalent substance

  3. Ionic substance

  4. Metallic substance

  5. Noble gas

Show answer
Correct Option: D
Explanation:

Metallic substance exists as cations with delocalized electrons.
The positive ions (cations) are arranged to form a kernel in the sea of delocalised electrons. The force of attraction between the positive ions (cations)  and  the sea of delocalised electrons is called the metallic bond.

Carbon combines with water to form:

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. water gas

  2. carbon gas

  3. hydrogen gas

  4. carbogen

Show answer
Correct Option: A
Explanation:

Carbon reacts with water to form water gas
$ C + H _2O \rightarrow CO + H _2$ 

Potassium reacts with water to form:

chemistry metals reaction of metals reactions of metals chemical properties of metals

  1. $KOH \  and \  H _2O$

  2. $KOH \ and \ H _2$

  3. $K(OH) _2 \ and  \ H _2O$

  4. $K(OH) _2 \ and \ H _2$

Show answer
Correct Option: B
Explanation:

$ 2K + 2H _2O \rightarrow 2KOH + H _2$