Class 7 Science MCQ Test-1

Explanation
Antacids are used for treating indigestion caused by overeating. They work by neutralizing excess stomach acid and providing relief from symptoms such as heartburn, bloating, and discomfort. Antibiotics are used to treat bacterial infections, analgesics are used for pain relief, and antiseptics are used to prevent infection in wounds. However, none of these medications specifically target indigestion caused by overeating like antacids do.

Explanation
The correct answer is B & C. Turmeric paper indicator and Phenolphthalein indicator both give a red or pink color on adding a basic solution. Turmeric paper turns red in the presence of bases, while Phenolphthalein indicator turns pink in basic solutions.

Explanation
Carbonic acid is a mineral acid because it is derived from minerals, specifically carbonates. It is formed when carbon dioxide dissolves in water, resulting in the formation of carbonic acid. Mineral acids are typically strong acids that can donate protons easily, and carbonic acid fits this definition. On the other hand, citric acid, acetic acid, and oxalic acid are organic acids that are derived from living organisms and do not fall under the category of mineral acids.

Explanation
Sodium Carbonate will give a basic solution on dissolving in water because it is a salt of a strong base (sodium hydroxide) and a weak acid (carbonic acid). When sodium carbonate dissolves in water, it dissociates into sodium ions and carbonate ions. The carbonate ions can accept protons from water molecules, resulting in the formation of hydroxide ions, which are responsible for the basic nature of the solution.

Explanation
Sodium hydroxide is a strong base because it completely dissociates in water to produce hydroxide ions (OH-) and sodium ions (Na+). This dissociation is almost 100% and results in a high concentration of hydroxide ions in solution, making it a strong base. Calcium hydroxide is also a base, but it is considered a weak base because it only partially dissociates in water. Sodium carbonate is a salt and Ammonium hydroxide is a weak base.