Which scientist is known for her work on radioactivity and the discovery of radium and polonium?
A. Dorothy Hodgkin
B. Marie Curie
C. Rosalind Franklin
D. Lise Meitner
Answer: Option B
Solution (By JKSSB Mock Tests)
Marie Curie, along with her husband Pierre, conducted pioneering research on radioactivity (a term she coined). In 1898, they discovered two new radioactive elements: polonium (named after her native Poland) and radium. She was the first woman to win a Nobel Prize and the only person to win in two different scientific fields (Physics and Chemistry).
Explanation:
Calcium (Ca²⁺) and magnesium (Mg²⁺) ions react with soap anions to form insoluble precipitates (scum), preventing lather. Sodium and potassium soaps are soluble and lather well. So detergents are preferred in hard water because their calcium/magnesium salts are soluble. Hardness is measured in terms of CaCO₃ equivalent.
Explanation:
Detergents (e.g., sulfonates) do not precipitate with Ca²⁺/Mg²⁺, so they lather well in hard water. Soaps form insoluble scum. This is a major advantage.
Explanation:
BOD stands for Biological Oxygen Demand. It is a measure of the amount of dissolved oxygen required by microorganisms to decompose the organic matter present in a water sample. High BOD indicates severe organic pollution and poor water quality for aquatic life.
No comments yet. Be the first to start the discussion!