Who is credited with the discovery of the atomic nucleus through the gold foil experiment?
A. Ernest Rutherford
B. James Chadwick
C. J. J. Thomson
D. John Dalton
Answer: Option A
Solution (By JKSSB Mock Tests)
Ernest Rutherford, in 1911, along with Geiger and Marsden, bombarded a thin gold foil with alpha particles. Most passed through, some were deflected at large angles, leading to the nuclear model of the atom—a small, dense, positively charged nucleus with electrons around it. Thomson's plum pudding model predicted no large deflections. Chadwick discovered neutron.
Explanation:
Amylase (present in saliva and pancreatic juice) hydrolyses starch into maltose and dextrins. Pepsin digests proteins in the stomach. Lipase breaks down fats. Trypsin also digests proteins. Enzymes are specific biocatalysts.
Explanation:
A small amount of ethanol (alcohol) is added to chloroform to inhibit its oxidation by air to toxic phosgene (COCl₂) and HCl. Ethanol acts as a negative catalyst (stabilizer) by consuming any formed phosgene. MnO₂, Pt, Fe are positive catalysts. Negative catalysts are also called inhibitors, used to prevent undesirable reactions.
Explanation:
Dalton proposed that all atoms of a given element are identical in mass and properties. The discovery of isotopes (atoms of same element with different mass) contradicted this. Dalton's theory explained the three laws of chemical combination. Later models modified the theory. Subatomic particles and radioactivity also could not be explained by Dalton.
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