eVidyaKosh: Class - 10: Science

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Write a balanced chemical equation with state symbols for the following reactions:

(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.

(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

Here are the balanced chemical equations with state symbols:

(i) Barium chloride (aqueous) + Sodium sulphate (aqueous) → Barium sulphate (solid) + Sodium chloride (aqueous) \[ \text{BaCl}_2(aq) + \text{Na}_2\text{SO}_4(aq) \rightarrow \text{BaSO}_4(s) + 2\text{NaCl}(aq) \] (ii) Sodium hydroxide solution (aqueous) + Hydrochloric acid solution (aqueous) → Sodium chloride solution (aqueous) + Water (liquid) \[ \text{NaOH}(aq) + \text{HCl}(aq) \rightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l) \] These equations include the state symbols, indicating the physical states of the reactants and products.

Write the balanced equation for the following chemical reactions:

(i) Hydrogen + Chlorine → Hydrogen chloride

(ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride

(iii) Sodium + Water → Sodium hydroxide + Hydrogen

Here are the balanced chemical equations for the given reactions:

(i) Hydrogen + Chlorine → Hydrogen chloride \[ \text{H}_2 + \text{Cl}_2 \rightarrow 2\text{HCl} \] (ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride \[ 3\text{BaCl}_2 + \text{Al}_2(\text{SO}_4)_3 \rightarrow 3\text{BaSO}_4 + 2\text{AlCl}_3 \] (iii) Sodium + Water → Sodium hydroxide + Hydrogen \[ 2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2 \]

Both reactions are now balanced with respect to the number of atoms of each element on both sides.

Why should a magnesium ribbon be cleaned before burning in the air?

Magnesium ribbon should be cleaned before burning to remove the thin layer of magnesium oxide that forms on its surface due to exposure to air. This oxide layer is stable and prevents the magnesium from reacting efficiently with oxygen during burning. By cleaning the ribbon, typically by rubbing it with sandpaper, you remove this oxide layer, allowing the magnesium to burn more readily and completely, producing a bright white flame and forming magnesium oxide.

Burning of a Magnesium Ribbon in Air and Collection of Magnesium Oxide in a Watch-Glass

The burning of a magnesium ribbon in air is a classic chemistry experiment that demonstrates the reaction between magnesium and oxygen to form magnesium oxide. Here’s a step-by-step guide:

Materials Needed:

Magnesium ribbon
Tongs
Bunsen burner or spirit lamp
Watch-glass
Sandpaper (optional, for cleaning the ribbon)

Procedure:

Preparation of Magnesium Ribbon: If the magnesium ribbon is tarnished (appears dull), use sandpaper to clean it by rubbing gently. This removes the oxide layer and ensures the ribbon burns more easily.
Lighting the Bunsen Burner: Light the Bunsen burner and adjust it to get a blue, non-luminous flame.
Burning the Magnesium Ribbon:
- Using tongs, hold one end of the magnesium ribbon and bring the other end into the flame. The magnesium ribbon will ignite, emitting a bright white light. Avoid looking directly at the flame, as the light is intense.
- As the magnesium burns, it reacts with oxygen in the air to form magnesium oxide (MgO).
Chemical Equation:
\[ 2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO} \]
Collection of Magnesium Oxide:** - Hold the burning ribbon over a watch-glass. As the reaction progresses, a white powder (magnesium oxide) will form and fall onto the watch-glass. - Once the ribbon has completely burned, place any remaining ashes or residue onto the watch-glass.
Observation:** - Observe the white powder (magnesium oxide) collected on the watch-glass. This powder is the product of the combustion of magnesium in oxygen.

Safety Precautions:

Do not look directly at the burning magnesium as it emits an intense light that can harm your eyes.
Handle the hot ribbon and magnesium oxide with care to avoid burns.
Conduct the experiment in a well-ventilated area.

This experiment vividly illustrates a chemical reaction involving combustion and the formation of a compound from an element and oxygen.