Magnesium ribbon was allowed to burn inside a given gas P leaving a white solid residue Q. Addition of water to Q liberated a gas which produced dense white fumes with a drop of hydrochloric acid. The gas P was?
nitrogen
chlorine
oxygen
sulphur (IV) oxide
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Given the information in the scenario, we can deduce the identity of gas P through a series of logical steps:
1. Magnesium ribbons burned in gas P, leaving a white solid residue Q. When magnesium burns, it typically reacts with oxygen to form magnesium oxide (MgO), which is a white solid. This suggests that gas P is likely to be oxygen (O2).
\[ 2Mg(s) + O_2(g) \rightarrow 2MgO(s) \]
2. When water is added to the white solid residue Q, a gas is liberated that produces dense white fumes with a drop of HCl. Adding water to magnesium oxide would produce magnesium hydroxide:
\[ MgO(s) + H_2O(l) \rightarrow Mg(OH)_2(aq) \]
3. Magnesium hydroxide is a base, and if it reacts further, it can release a gas. The only common gaseous product that would be released from reacting a base like magnesium hydroxide with an acid (such as the components of HCl in the air) is ammonia (NH3). This is because magnesium hydroxide can react with more water to form magnesium ions and hydroxide ions, which can then react with ammonium ions (from traces of ammonium salts) to release ammonia gas.
\[ Mg(OH)_2(aq) + 2NH_4^+ \rightarrow Mg^{2+} + 2NH_3(g) + 2H_2O(l) \]
4. The dense white fumes produced when this gas comes into contact with HCl are characteristic of the reaction between ammonia and hydrochloric acid, forming the white smoke of ammonium chloride (NH4Cl), as mentioned earlier.
Therefore, the gas P that allowed the magnesium ribbons to burn and form a white solid residue Q is oxygen (O2). The white solid residue Q is magnesium oxide (MgO), and the gas released upon the addition of water is ammonia (NH3), which reacts with HCl to produce white fumes of ammonium chloride.
if magnesium ribbon burns in Nitrogen it forms Mg3N2 this Magnesium nitride on reaction with water yields ammonia ammonia and HCl is a blast of dense white fumes of ammonium chloride
The correct answer is **C. oxygen**.
When magnesium ribbon burns, it reacts with oxygen to form magnesium oxide (MgO), which is the white solid residue Q. The addition of water to magnesium oxide forms magnesium hydroxide (Mg(OH)₂), which then reacts with hydrochloric acid (HCl) to produce dense white fumes of ammonium chloride (NH₄Cl). This reaction is characteristic of ammonia (NH₃) coming into contact with hydrochloric acid. Therefore, the gas P that allowed the magnesium ribbon to burn and form the white solid residue Q is oxygen (O₂).
The correct answer is B. chlorine.
When magnesium ribbon burns in chlorine gas, it produces magnesium chloride (MgCl2), which is a white solid residue.
Mg (s) + Cl2 (g) → MgCl2 (s)
Adding water to MgCl2 liberates hydrogen chloride gas (HCl).
MgCl2 (s) + H2O (l) → Mg(OH)2 (s) + 2HCl (g)
The hydrogen chloride gas reacts with the moisture in the air to produce dense white fumes.
HCl (g) + H2O (l) → H3O+ (aq) + Cl- (aq)
Adding a drop of hydrochloric acid (HCl) to the fumes will enhance the reaction and produce more dense white fumes.
So, the gas P is chlorine (Cl2).
B
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You are all stupid. How do you expect ammonia to be evolved from magnesium hydroxide. Doesn't it sound weird even to you?
