Chapter: Basic Concepts of Chemistry
Which one of the following is the correct reactivity series with water?
The reactivity of metals with water follows a specific order, defined by their position in the reactivity series, which ranks metals based on their ability to displace hydrogen from water and form hydroxides.
Metals react with water producing hydroxides and hydrogen gas. The general reaction is:
For example, when Zinc reacts with water, the reaction is as follows:
This illustrates that Zinc can react with water, but Copper cannot react under normal conditions. Iron and Lead have lesser reactivity compared to Zinc when discussing water displacement.
For remembering the reactivity series with water, use the mnemonic: “Please Send My Cat Home” for Potassium, Sodium, Magnesium, Calcium, and then Iron, Zinc, Lead, and Copper.
A comparison table can effectively present the reactivity of metals with water, illustrating which metals can and cannot react, alongside their respective byproducts (hydroxides and hydrogen gas).
Verified against NCERT Class 10 Science, Chapter 3 (Acids, Bases, and Salts).
Which one of the following statements about water is not true?
Water (H2O) is a polar molecule because of its bent shape and the difference in electronegativity between hydrogen and oxygen, leading to a permanent dipole moment.
In water:
Remember, "Water is Polar" to recall its molecular structure and properties related to hydrogen bonding.
Verified against NCERT Class XI Chemistry, Chapter 2 (Structure of Atom).
Which one of the following metals does NOT react with cold water ?
Metals react with water based on their position in the reactivity series. Metals like potassium and sodium are more reactive than magnesium and readily react with cold water.
Reactivity towards water can be summarized as:
A brief review of the other options:
Remember: "King Size Noodles Can" - K (Potassium) and Na (Sodium) react; Mg (Magnesium) does not.
Verified against NCERT Class 10 Science, Chapter 3 (Metals and Non-metals).
Which one of the following pairs of elements is liquid at room temperature and at normal pressure?
The physical properties of elements are influenced by their molecular structure and intermolecular forces. At normal room temperature (25°C) and pressure (1 atm), Mercury (Hg) and Bromine (Br₂) remain in liquid state due to their unique physical properties.
Mercury is a heavy metal, a dense liquid at room temperature, characterized by a melting point of -38.83°C. Meanwhile, Bromine, a halogen, is a reddish-brown liquid which melts at -7.2°C. Both substances remain liquid under typical atmospheric conditions.
- **Option (a) Gallium and Bromine**: Gallium solidifies at 29.76°C. Only Bromine remains liquid.
- **Option (c) Gallium and Mercury**: Both exhibit different states at room temperature; Gallium is solid.
- **Option (d) Gallium and Caesium**: Caesium is solid at room temperature.
Remember the mnemonic: "Mercury-Bromine, Liquid Team!" Both are the only liquid pair at room temperature.
A comparative melting point chart highlighting the states of elements at room temperature can help visualize which elements remain liquid.
Verified against NCERT Class XI Chemistry, Chapter 1 (Some Basic Concepts of Chemistry)
What is the number of water molecules present in a Ferrous Sulphate crystal?
A diagram comparing anhydrous Ferrous Sulphate and Ferrous Sulphate heptahydrate, illustrating structural differences with labeling for the seven water molecules.
Verified against NCERT Class X Chemistry, Chapter on Salts and Crystallization.
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