Test: Chemistry - 7 - MCAT MCQ

6*10⁴ = 6000 has only one significant figure. Leading zeros are not significant, for 0.008320 it is 4. Zeros appearing anywhere between two non-zero digits are significant figures, for 4.05*10^-2 = 0.00405, it is 3. Trailing zeros in a number containing a decimal point are significant, for 100.0 it is 4.

Freezing – liquid to solid, melting – solid to liquid, sublimation – solid to vapour, condensation – gas to liquid, deposition – gas to solid.

The sum of oxidation numbers in polyatomic ion or species is equal to the charge of the ion. For example, the sum of the oxidation number for SO₄^2- is -2.

Number of valence electrons in N is 5 and in H it is 4.
So total number of valence electrons = 5 + 4 = 9; Charge = +1.
Therefore, total electrons in NH₄⁺ = 9 - 1 = 8
When the total number of electrons is less than 8, divide by 2. If it lies between 9 and 56, divide it by 8.
8/2 = 4; X = 4
Therefore, hybridisation in NH₄⁺ is sp³.

Aprotic solvents do not solvate the anions effectively and it is used for S_N² reactions. Acetonitrile is the only aprotic solvent whereas others are polar protic solvents.

The most intense peak is called as base peak. It usually corresponds to the molecular ion only, if the spectra are recorded at low ionization energy.

KCl is highly soluble because its solubility is greater than 0.1M. AgCl is sparingly soluble because its solubility is less than 0.01 M. PbS is least sparingly soluble becauseits solubility is very much less than 0.01 M.

For an ideal gas, PV = constant, at constant temperature. The internal energy of a given quantity of an ideal gas at a constant temperature is independent of its volume, thus (∂U/∂V)T = 0.

By applying Ideal gas equation, V = nRT/P
At STP, P = 1 atm, n = 1mol, R = 0.082 L atm K^-1 mol^-1, T = 273K
V = (1*0.082*273)/273 = 22.38 L = 22.4 L

Molarity (M_A) = n_A/ volume in litres.
Normality = Gram equivalent of A/Volume in litres of solution.
Mole fraction (χi) = ni/ (n₁+n₂+n₃....).
Parts per million (ppm) = (Mass of A/Total mass) x 10⁶

For a non-spontaneous or non-feasible process, ΔH > 0 and ΔS < 0. For a spontaneous or irreversible reaction, ΔH < 0 and ΔS > 0. For an equilibrium or reversible process, ΔH = 0 and ΔS = 0.

The value of screening constant (S) and effective nuclear charge (Z*) can be calculated using Slater's rule. Effective charge (Z*) = Z – S (where Z- atomic number and S-screening constant).

Glass equipments are divided into two; with ground-glass joints and without ground-glass joints. Separating funnel is the only glass equipment with ground-glass joints.

The electronegativity and atomic size of iodine is larger so there is a weaker bond between hydrogen and iodine that makes the electron cloud much lesser than H-F bond. So, H-I is the weakest base; in other words it is the strongest acid.

Oxidation: Cu→Cu²⁺ + 2 e^- E^o_ox = -(0.340 V) Reduction: Ag⁺ + e- → Ag E^o_red = 0.799 V Overall cellreaction is Cu(s) + 2 Ag⁺(aq)→ Cu²⁺ (aq) + 2 Ag(s) E⁰_cell = E⁰_red + E⁰_ox = 0.799 V + (-0.340 V) = 0.459V Nernst equation, E_cell = E⁰_cell – (0.0256/n) (In_ox/In_red) = 0.459 –(0.0256/2) * In [0.024 / (0.0048)²] = 0.459 – 0.0128 * In (1043) = 0.459 – 0.0128 * 6.95 E_cell = 0.370 V