Test: Chemistry - 6 - MCAT MCQ

Method is as follows:
Molecular formula for sodium sulphate is Na₂SO₄
Molar mass of sodium sulphate is 44 + 32 + 64 = 140
Mass percent of sodium is (2*22) / (140) * 100 = 31.4
Mass percent of sulphur is (1*32) / (140) * 100 = 22.8
Mass percent of oxygen is (4*16) / (140) * 100 = 45.7

An exothermic reaction is characterized by the release of heat energy into the surroundings. For instance, the burning of gasoline exemplifies an exothermic reaction because it generates both heat and combustion products. On the other hand, the process of melting ice (option b) is classified as endothermic since it necessitates the absorption of heat energy to convert ice into liquid water. Similarly, photosynthesis (option c) is an endothermic process wherein plants convert sunlight energy into chemical energy. Lastly, the dissolution of salt in water (option d) is also an endothermic process, but it does not release as much heat energy as the burning of gasoline.

• Hot water in a thermos flask serves as an illustration of an isolated system, wherein neither energy nor matter can enter or exit.
• Boiling soup in an open saucepan on a stove is an example of an open system since it can freely exchange both energy and matter with its surroundings.
• Cooking rice in a pressure cooker represents a closed system in which it can solely exchange energy with its surroundings, but not matter.
• A pot of boiling water and an open tank of water demonstrate an open system as matter can be exchanged with the surroundings.

The ionisation energy depends upon the atomic radius. As the s-orbital electrons remain closer to the nucleus, the ionisation energy will be greater for s- orbital than for p-, d- and f- orbitals.

Florence flask is used for mixing of organic chemicals. It is commonly called as round-bottom flask or boiling flask. Its narrow neck prevents the splash exposure.
Erlenmeyer flask is used for volumetric titration. It is also called as conical flask.
Buckner funnel is used for vacuum filtration.

In an acid-base equilibrium, the reaction always favours the formation of the weakest acid and the weakest base due to their stability. The weakest acid and the weakest base must always be on the same side of the reaction.

Given data: λ = 1.55, d = 4.04 A⁰
For second order reflection n = 2,
Bragg equation is 2d sin Θ = 2λ
Θ = sin^-1(λ/d) = sin^-1(0.381) = 22⁰ 24'

When pressure increases, volume gets decreased. Graph of pressure Vs volume gives curve. P₁ * V₁ = P₂ * V₂.

When a decomposition reaction involves redox reactions; it is called asinternal redox reaction, because the oxidized and reduced elements originate in the same compound. N in NH₄⁺ is oxidized from -3 to 0 and N in NO₂^- is reduced from +3 to 0. Both redox reactions occur in the same NH₄NO₂ molecule.
Ex: NH₄NO_2(s) → N_2(g) + 2 H₂O_(g)
In single displacement reactions, atom of one reactant replaces the atom of the other reactant.
Ex: a A + b BC → c AC + d B
In simple redox reaction,oxidation numbers of ionic reactants are changed by the direct transfer of electrons from one ion to the other.
Ex: 2 Fe³⁺_(aq) + Sn²⁺_(aq) → 2 Fe²⁺_(aq) + Sn⁴⁺_(aq)
In a disproportionation reaction, the same species will simultaneously get oxidised and reduced to form two different products.

The electronic configuration of helium in the ground state is represented as (σ_1s)² and in the excited state, it is represented as (σ* _1s)².
So, number of electrons in bonding molecular orbital (N_b) is 2 and number of electrons in antibonding molecular orbital (N_a) is 2.

The bond order for He₂ is 0, so the molecule does not exis

When the number of R groups in the carbon atoms gets increased, the reactivity of S_N² reactions will be decreased. So, methyl halide will undergo faster S_N² reaction than primary, secondary and tertiaryalkyl halides. Tertiary alkyl halide does not undergo S_N² reaction because of steric hindrance.

The intensity of signals in proton NMR is directly proportional to the total number of protons present in the molecule. The number of signals corresponds to the different types of protons present in the molecule. The position of signals reflects the chemical shift and the magnetic environment experienced by the protons. The splitting of signals indicates the presence of adjacent atoms that have a different number of protons.

It's an unusual compound, in which oxygen takes the positive oxidation number +2. Because F is more electronegative than O, therefore F gets the -1 oxidation state and O gets the positive oxidation state.

Surface tension is generally expressed in terms of dyne cm^-1. In SI unit, surface tension is expressedin terms of N m^-1.

Metal deficiency defect is due to cation vacancy. Schottky defect is commonly found in ionic crystals in which cations and anions are of similar size. Frenkel defect is shown by ionic crystals of different size. Metal excess defect is due to anion vacancy and interstitial cation. In line defect, groups of atoms are arranged in an irregular position.