Who proposed the atomic theory of matter, stating that all matter is composed of indivisible atoms?
A. John Dalton
B. J.J. Thomson
C. Dmitri Mendeleev
D. Ernest Rutherford
Answer: Option A
Solution (By JKSSB Mock Tests)
John Dalton proposed the atomic theory in 1803. His theory stated that all matter is made of indivisible and indestructible atoms, atoms of a given element are identical in mass and properties, and compounds are formed by combinations of different atoms in fixed ratios.
Explanation:
Mendeleev named the missing element eka-aluminium. When gallium was discovered (1875), its properties (density, oxide formula) closely matched Mendeleev's predictions, validating his table. Germanium was eka-silicon; scandium was eka-boron. These predictions were a triumph of the periodic law. Gallium has a low melting point (~30°C) and is used in semiconductors. Mendeleev corrected atomic masses based on group properties.
Explanation:
Dilute HNO₃ is an oxidizing agent; it oxidizes the hydrogen produced to water and itself gets reduced to nitrogen oxides (NO, N₂O, etc.). Very dilute HNO₃ with Mg/Mn can produce H₂. Metals above hydrogen normally displace H₂ from non-oxidizing acids like HCl.
Consider the following statements: 1. Specific conductance decreases with dilution. 2. Equivalent conductance increases with dilution. Which is/are correct?
Explanation:
Specific conductance (conductivity) is the conductance of a 1 cm³ solution. It decreases with dilution because the number of ions per unit volume decreases. Equivalent conductance is the conductance of all ions produced by 1 gram equivalent of electrolyte. It increases with dilution because the ions have more space to move, reducing interionic attractions.
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