Indian Navy AA (Artificer Apprentice) Chemistry — practice by topic

Boyle's law: at fixed $T$ and $n$, $PV = $ constant, so $P \propto 1/V$. Squeeze a gas into half the volume at constant temperature and its pressure doubles. The $P$-$V$ curve at fixed $T$ is a hyperbola called an isotherm. Option A is the opposite (direct proportion), which would mean compressing a gas reduces its pressure — physically absurd.

Electronegativity increases across a period and decreases down a group. The Pauling-scale values for period 2 nonmetals: - C: 2.55 - N: 3.04 - O: 3.44 - F: 3.98 (highest of any element) So the correct ascending order is **C < N < O < F**. Option A reverses everything. Option C breaks the trend by putting F before O. Memory aid: "FONClBrISCHP" is the electronegativity ladder from highest to lowest among common nonmetals (F first, P last among this set).

Balmer series corresponds to transitions terminating in $n_1 = 2$. The first four lines ($n_2 = 3, 4, 5, 6$ to $n_1 = 2$) lie at approximately $656\,\text{nm}$ (H$_\alpha$, red), $486\,\text{nm}$ (H$_\beta$, blue-green), $434\,\text{nm}$ (H$_\gamma$, blue) and $410\,\text{nm}$ (H$_\delta$, violet), all in the visible range.