Correct Answer: B

Rationale: The atomic number of neon is 10, which represents the number of protons in its nucleus. In a neutral atom, the number of electrons is equal to the number of protons to maintain electrical neutrality.
Therefore, a neutral atom of neon contains 10 electrons, matching the 10 protons within the nucleus.
Choice A (9 electrons) is incorrect as it doesn't correspond to the atomic number of neon.

Choices C (11 electrons) and D (12 electrons) are also incorrect as they do not align with the correct atomic number of neon.

Correct Answer: B

Rationale: The correct name of MgO is Magnesium oxide. Mg represents the chemical symbol for magnesium, and O represents the chemical symbol for oxygen. When these elements combine, they form magnesium oxide. Option A, Manganese oxide, is incorrect as it refers to a compound of manganese and oxygen, not magnesium. Option C, Magnesium oxate, is not a valid chemical compound name. Option D, Magnesium hydroxide, refers to a different compound consisting of magnesium, oxygen, and hydrogen.

Correct Answer: C

Rationale: The correct formula for sodium nitrate is NaNO₃. In this formula, 'Na' represents sodium, 'N' represents nitrogen, and 'O₃' represents three oxygen atoms. Sodium nitrate consists of one sodium ion (Na⁺) and one nitrate ion (NO₃⁻), which means the correct formula is NaNO₃.
Choice A (NaNO) is incorrect as it lacks the subscript indicating the presence of three oxygen atoms.
Choice B (Na NO) is incorrect as it includes a space between 'Na' and 'NO', which is not part of the standard chemical formula notation.
Choice D (Na NO₂) is incorrect as it indicates a different compound with a nitrite ion (NO₂⁻) instead of nitrate ion.

Correct Answer: D

Rationale: Lemon juice is the correct answer as it is acidic in nature. Acids like lemon juice release hydrogen ions when dissolved in water, which causes litmus dye to change color from blue to red. Milk (
Choice
A) is neutral, sea water (
Choice
B) is slightly alkaline, and ammonia (
Choice
C) is a base.
Therefore, these substances do not cause litmus dye to change from blue to red.

Correct Answer: C

Rationale: Potassium iodide (KI) shows a decrease in solubility in water with an increase in temperature. This is due to the dissolution of KI in water being an endothermic process. When the temperature rises, the equilibrium shifts toward the solid state, leading to a decrease in solubility.
Therefore, as the temperature increases, KI becomes less soluble in water.


Choice A (NaCl) and
Choice D (CaCl) do not exhibit a decrease in solubility with an increase in temperature. NaCl and CaCl are generally more soluble in water at higher temperatures.
Choice B (Oxygen) is a gas and not typically considered in solubility discussions involving solids or liquids dissolving in water.