Test: Chemistry - 8 - MCAT MCQ

From the Trouton's law ΔH/T_b = 88 J mol^-1 K^-1
The given data is T_b = 80°C = 80 + 273 = 353 K
Therefore, ΔH = (88J mol^-1 K^-1) (353 K) = 31064 J mol^-1 = 31.064 kJ mol^-1 

Each sphere in hcp structure is in contact with 12 neighbouring spheres. Six spheres are on its own layer, three on the above layer and remaining three on the below layer. So, the coordination number of hcp structure is 12. For BCC structure it is 8. For ZnO it is 4.

It keeps the solution of two half-cells electrically neutral. In anodic half-cell, positive ions will accumulate around the anode due to deposition of negative ions by oxidation. To neutralise these positive ions, sufficient number of negative ions are provided by salt bridge. Similarly for cathodic halfcell, it is vice-versa.

In Al₂ Cl₆ lone pairs of electron from chlorine are donated to electron deficient aluminium in such a way that it is held together by dative bond, where aluminium acts as an electron acceptor and chlorine acts as an electron donor. AlBr₃ is a neutral ionic molecule. NaCl^- ionic bond, C₂ H₆ - covalent bond,H₂ O₂– Hydrogen bond.

The polarisation of the bond is due to electron withdrawing or electron donating effect of adjacent atoms or groups. Such a type of electron displacement along a carbon chain is called Inductive effect.
Eg: C –>--- C –>--- C –>--- C₆ H₅
The electron withdrawing nature of groups or atoms is called negative inductive effect. C₆H₅ is the only group, which has –I effect. Since --C₆ H₅ is electronwithdrawing group, it pulls up the electrons towards itself. Thereby it creates a partial positive charge in adjacent carbon atoms and partial negative charge in phenyl group (C₆ H₅).

The spots of colorless compounds can be detected by placing the T.L.C plate in a closed jar containing few crystals of iodine. Spots of compounds, which absorb iodine, will indicate as a brown color.

A pure chemical compound exhibits a consistent boiling point, meaning it vaporizes entirely at that specific temperature without undergoing any alterations in its composition. This phenomenon is often referred to as a constant boiling mixture.

Among the mentioned properties, density stands as the sole intensive property, while all other properties are extensive properties. An intensive property of a system remains unaffected by the quantity of substance present within the system. In contrast, an extensive property of a system varies based on the amount of substance or substances present in the system.

Due to very high kinetic energy, gaseous particles easily escape from the attractions of other particles and tend to maintain very long distances from each other. So, the attraction between gaseous particles is negligible.

Diamond consists of atoms that are interconnected through a continuous network of covalent bonds. Ionic crystals, on the other hand, are formed by the attraction between atoms held together by ionic bonds. Metallic crystals are characterized by atoms being bound through metallic bonds. In molecular crystals, molecules are connected by relatively weak Van der Waals forces.

Hess's law states that the enthalpy or heat energy change accompanying a chemical reaction is independent of the pathway between the initial and final states. ΔH for a single reaction can be calculated from the difference between the enthalpy (heat) of formation of the product and reactant.
ΔH⁰ reaction = Σ ΔH_f⁰ (products) – Σ ΔH_f⁰ (reactant)

Atomic radii decrease across the period. Cations are smaller than their parent atoms. Among these isoelectronic ions, the one with larger positive nuclear charge will have the smaller radius. So, here the largest atom is Mg and the smallest one is Al³⁺.

Guessing the correct value between two calibrated marks on the metre scale is an example for interpolation error. It is one of the two types of human or personal errors. Incorrect identification of indicator's color change in titration – Operative error. Zero setting of the needle in analog display – static error. Calibration of measured instrument - Instrument error.

The Henderson-Hasselbalch equation explains whether a compound will exist in its acidic form or in its basic form at a particular pH. [A^-] = Molar concentration of a conjugate base. [HA] = Molar concentration of an undissociated weak acid (M).

A quasi-static process is the one in which the system may be considered to be in equilibrium at all times.