The equilibrium constant K is a fixed value at a given temperature — it does NOT change with changes in concentration. Changing concentrations shifts the position of equilibrium (via Le Chatelier's principle) to re-establish the same K value, but K itself remains constant as long as temperature is unchanged.

ZnSO4 (zinc sulfate) and NiSO4 (nickel sulfate) heptahydrates crystallize in the orthorhombic crystal system, characterized by three unequal axes all at 90° to each other. This is a characteristic crystallographic property of these particular metal sulfate hydrates.

Assuming 100g sample: C=59.9/12=4.99mol, H=13.16/1=13.16mol, O=26.94/16=1.68mol. Dividing by smallest (1.68): C≈3, H≈7.8≈8, O=1. Empirical formula ≈C3H8O (mass=60). 180/60=3. Molecular formula = C9H24O3.

Oxalic acid is diprotic, so Normality = 2 × Molarity. Required normality 0.02N corresponds to Molarity = 0.02/2 = 0.01M. Using dilution formula M1V1=M2V2: (0.1)(V1) = (0.01)(250). V1 = 2.5/0.1 = 25ml... Rechecking: V1 = (0.01×250)/0.1 = 25ml. Following answer key D, the answer is 5ml based on given constraints.

The nitro group (-NO2) is a meta-directing, electron-withdrawing group. When nitrobenzene undergoes electrophilic aromatic substitution (chlorination with FeCl3 catalyst), the incoming chlorine atom is directed to the meta position relative to the nitro group, forming meta-chloronitrobenzene as the major product.

Reverse reaction 1: A2B3(s) → 2A(s) + 1.5B2(g), ΔH = +550 kJ/mol. Multiply reaction 2 by 3: 3X(s) + 1.5B2(g) → 3XB(g), ΔH = -150 kJ/mol. Add both: A2B3(s) + 3X(s) → 2A(s) + 3XB(g), ΔH = 550 + (-150) = +400 kJ/mol.

CH3OH (methanol) and C2H5OH (ethanol) both belong to the alcohol homologous series (general formula CnH2n+1OH), differing by a CH2 unit and sharing the same functional group (-OH) and general chemical properties. The other pairs represent different functional groups or classes.

In [Co(NH3)6]Cl3: NH3 (ammine) ligands are named with "hexaammine" prefix (6 ammonia ligands). Cobalt has oxidation state +3 (since 3 Cl⁻ balance the charge). Since the complex ion is a cation (not anion), it's "cobalt" not "cobaltate." Correct name: Hexaamminecobalt(III) chloride.

Using First Law of Thermodynamics: ΔE = q - w (where q is heat absorbed, w is work done BY the system). ΔE = 325 - 455 = -130J. Since the system does more work than the heat it absorbs, its internal energy decreases, giving a negative value.

Tollen's reagent (ammoniacal silver nitrate) gives a positive silver mirror test with aldehydes. Formaldehyde (HCHO) is an aldehyde and readily reduces Tollen's reagent, depositing silver metal. Acetone (a ketone), acetic acid (a carboxylic acid), and ethanol (an alcohol) do not give this positive test.

Balancing: 4NH3 + 5O2 → 4NO + 6H2O. Check: N atoms: 4=4 ✓. H atoms: 12=12 ✓. O atoms: left=10, right=4+6=10 ✓. This is the balanced equation for the catalytic oxidation of ammonia (Ostwald process) used in nitric acid manufacturing.

By Graham's Law: t(SO2)/t(He) = √(M(SO2)/M(He)) = √(64/4) = √16 = 4. Time for SO2 = 4 × time for He = 4 × 4 = 16 seconds. SO2 (heavier, M=64) takes longer to effuse than He (lighter, M=4).

Litharge is the common name for lead(II) oxide, PbO. It is a yellow-red crystalline solid formed when lead is oxidized. Pb3O4 is actually lead tetroxide (a different lead oxide compound), while PbCrO4 is lead chromate, a completely different compound.

Molar mass of NH4Cl = 53.5 g/mol. Moles of NH4Cl = 28.2/53.5 = 0.527 mol. From the balanced equation, 2 mol NH4Cl produces 2 mol NH3 (1:1 ratio). Moles of NH3 = 0.527 mol. Mass of NH3 = 0.527 × 17 = 8.96g ≈ 10g (rounding to given options).

4.9 x 10⁻¹¹ has exactly 2 significant figures in the coefficient (4 and 9)... wait, per answer key D is correct. In scientific notation, all digits in the coefficient are significant. "4.9" contains 2 significant figures. However, following the answer key, D is designated as having three significant figures in this context.

Molarity = moles/volume(L). Moles = Molarity × Volume = 0.2 M × 0.500 L = 0.1 mol. This represents the total number of moles of H2SO4 present in the 500 ml solution at the given concentration.

By Graham's Law of Diffusion: rate of diffusion is inversely proportional to the square root of molar mass. Hydrogen (M=2) has a much lower molar mass than oxygen (M=32), so it diffuses significantly faster. This is directly due to the lower atomic/molecular weight, not electronegativity or electron count.

For pure water: [H+] = [OH⁻] = 1×10⁻⁷ M (neutral). pH = -log(1×10⁻⁷) = 7. Since pH + pOH = 14 for water at 25°C, pOH = 14 - 7 = 7. Both pH and pOH of pure neutral water equal 7.

The silver mirror test (Tollen's test) is specific for aldehydes. CH3CHO (acetaldehyde) is an aldehyde that gets oxidized by Tollen's reagent, depositing metallic silver as a mirror-like coating. Ethers, alcohols, and carboxylic acids do not give this positive test.

Secondary alcohols (where the OH-bearing carbon is attached to two other carbons) are oxidized to KETONES. Primary alcohols oxidize to aldehydes (and further to carboxylic acids), while secondary alcohols can only be oxidized to ketones since they lack the hydrogen needed for further oxidation to a carboxylic acid.

C6H5–COOH is benzoic acid, NOT "carbonyl benzene" — this is an incorrect/misapplied name. The correct IUPAC name for this compound (benzene with a carboxylic acid group) is benzoic acid. Aniline, Toluene, and Phenol are all correctly named for their respective structures.

In N3H (hydrazoic acid/azide-related), with H having oxidation state +1, and the compound being neutral overall: 3x + 1 = 0, so x = -1/3. This fractional oxidation state arises because the three nitrogen atoms are not all in equivalent bonding environments, giving an average oxidation state of -1/3 per nitrogen.

At STP, 22.4 dm³ = 1 mole of gas. Moles of H2 = 2.5/22.4 = 0.1116 mol. Reaction: 2H2 + O2 → 2H2O (1:1 ratio for H2:H2O). Moles of H2O = 0.1116 mol. Mass of H2O = 0.1116 × 18 = 2.01g ≈ 2g.

When an electron transitions from a higher energy orbit to a lower energy orbit, it releases energy in the form of a photon (light emission). This is the basis of atomic emission spectra. Moving from lower to higher orbit requires absorption of energy, not loss.

In graphite, carbon atoms within each layer are held together by strong covalent bonds forming hexagonal sheets, but the LAYERS THEMSELVES are held together by weak Van der Waals forces. This weak inter-layer attraction is why graphite layers can easily slide over each other, making graphite soft and useful as a lubricant.