Chemistry - Study Mode
[#661] Curd is sour due to presence of
Correct Answer
(B) Lactic acid
Explanation
Solution: Curd is sour in taste due to the presence of lactic acid.
[#662] Drinking soda is
Correct Answer
(B) Acidic
Explanation
Solution: Drinking soda is acidic.
[#663] Muscle fatigue is caused by the accumulation of :
Correct Answer
(B) Lactic acid
Explanation
Solution: It was once believed that lactic acid build-up was the cause of muscle fatigue. The assumption was lactic acid had a "pickling" effect on muscles, inhibiting their ability to contract. Produced as a by-product of fermentation, lactic acid can increase intracellular acidity of muscles. This can lower the sensitivity of contractile apparatus to Ca 2+ but also has the effect of increasing cytoplasmic Ca 2+ concentration through an inhibition of the chemical pump that actively transports calcium out of the cell. This counters inhibiting effects of potassium on muscular action potentials.
[#664] The material used in the manufacture of lead pencil is
Correct Answer
(A) Graphite
Explanation
Solution: Pencils create marks via physical abrasion, leaving behind a trail of solid core material that adheres to a sheet of paper or other surface. They are noticeably distinct from pens, which dispense liquid or gel ink that stain the light colour of the paper. Most pencil cores are made of graphite mixed with a clay binder, leaving grey or black marks that can be easily erased. Graphite pencils are used for both writing and drawing, and the result is durable: although writing can usually be removed with an eraser, it is resistant to moisture, most chemicals, ultraviolet radiation and natural aging. Other types of pencil core are less widely used. Charcoal pencils are mainly used by artists for drawing and sketching.
[#665] Water can be separated from alcohol water mixture by
Correct Answer
(C) Distillation
Explanation
Solution: To separate a mixture of alcohol (ethanol) and water, you can use a process known as fractional distillation. This technique relies on the fact that the compounds in the mixture have different boiling points. Since ethanol boils at a lower temperature (78.5 degrees Celsius) than water, the alcohol vaporizes while most of the water remains a liquid.