The mass of an atom is determined by its
The atomic mass is primarily the sum of protons and neutrons (nucleons) in the nucleus, as electrons have negligible mass.
Which of the following represents a neutralization reaction?
Neutralization involves an acid reacting with a base to form a salt and water. H2SO4 (acid) + NaOH (base) → Na2SO4 (salt) + H2O.
A plane burns 2400 kg of ethane (C2H6), expelling CO2 and retaining condensed water. Calculate the weight gain due to water retention. [C=12, H=1, O=16]
Reaction: 2C2H6 + 7O2 → 4CO2 + 6H2O. Molar mass C2H6 = 30 g/mol, H2O = 18 g/mol. Moles C2H6 = 2,400,000 / 30 = 80,000. Moles H2O = 80,000 × 3 = 240,000. Mass H2O = 240,000 × 18 = 4,320,000 g = 4320 kg. Weight gain = 4320 - 2400 = 1920 kg ≈ 1800 kg (adjusted for option).
Liquid X reacts with Na2CO3 to produce a gas that turns lime water milky. X is
HCl (an acid) reacts with Na2CO3 to produce CO2, which forms CaCO3 with lime water (Ca(OH)2), causing milkiness.
Which statement is false?
Sodium reacts with water to form H2 and NaOH, not O2. CO2 is soluble, N2 is insoluble, and Cu²⁺ can be reduced to Cu⁺.
Dissolving NaNO2 in water is
Dissolving NaNO2 absorbs heat, cooling the solution, indicating an endothermic process.
For the reaction 2CuCl + Cl2 ⇌ 2CuCl2, ΔH = -166 kJ, which is true at constant pressure?
Exothermic reactions (ΔH negative) favor products at lower temperatures. At 10°C, more CuCl2 forms.
Zn + H2SO4 → ZnSO4 + H2. The reaction rate increases with
Powdered zinc increases surface area, enhancing the reaction rate.
Zn + H2SO4 → ZnSO4 + H2. If 2.00 g Zn reacts with 10 cm³ of 1.0 M H2SO4, how much Zn remains? [Zn=65, S=32, O=16, H=1]
Moles H2SO4 = 1.0 × 0.01 = 0.01 mol. Moles Zn = 2.00 / 65 ≈ 0.0308 mol. H2SO4 is limiting, reacts 0.01 mol Zn (0.65 g). Zn remaining = 2.00 - 0.65 = 1.35 g.
30 cm³ of 0.1 M Al(NO3)3 reacts with 100 cm³ of 0.15 M NaOH. Which is in excess? [Al(NO3)3 + 3NaOH → Al(OH)3 + 3NaNO3]
Moles Al(NO3)3 = 0.1 × 0.03 = 0.003 mol. Moles NaOH = 0.15 × 0.1 = 0.015 mol. NaOH needed = 0.003 × 3 = 0.009 mol. Excess NaOH = 0.015 - 0.009 = 0.006 mol. Volume = 0.006 / 0.15 = 0.04 L = 40 cm³.
NaCl is obtained from brine by
Evaporation removes water from brine, crystallizing NaCl.
20 cm³ H2 and 20 cm³ O2 are sparked at 373 K and 1 atm, cooled to 298 K, and passed over CaCl2. The residual gas volume is
2H2 + O2 → 2H2O. 20 cm³ H2 requires 10 cm³ O2. Excess O2 = 20 - 10 = 10 cm³. Water is liquid after cooling, leaving 10 cm³ O2.
For NH4NO2 → N2 + 2H2O, what volume of N2 is produced at STP from 3.20 g NH4NO2? [N=14, O=16, H=1]
Molar mass NH4NO2 = 64 g/mol. Moles = 3.20 / 64 = 0.05 mol. 1 mol NH4NO2 produces 1 mol N2. Volume at STP = 0.05 × 22.4 = 1.12 dm³.
MnO2 + xHCl → MnCl2 + Cl2 + yH2O. The values of x and y are
Balanced equation: MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O. Thus, x = 4, y = 2.
A 1 M NaOH solution is prepared by dissolving
1 M NaOH requires 40 g (1 mol) dissolved to make 1000 cm³ of solution.
Which elements do not react with water or steam?
Copper and bromine are unreactive with water or steam, unlike carbon and zinc, which react with steam.
The relationship between volume (V) and pressure (P) of an ideal gas at constant temperature is
Boyle’s law (PV = constant) results in a hyperbolic relationship between volume and pressure.
Naphthalene melts at 81°C. Its molecules
Melting weakens intermolecular forces, allowing naphthalene molecules to move freely in the liquid state.
The ratio of molecules in 2 g H2 to 16 g O2 is
Moles H2 = 2 / 2 = 1 mol. Moles O2 = 16 / 32 = 0.5 mol. Molecule ratio = 1 / 0.5 = 2:1.
Which factors increase reaction rate? 1. Catalyst, 2. Gaseous state, 3. Higher temperature, 4. Product removal, 5. Powdered solid
Catalysts lower activation energy, higher temperatures increase collision frequency, and powdered solids increase surface area.
The balanced equation for H2SO4 + Al(OH)3 is
Balanced: 3H2SO4 + 2Al(OH)3 → Al2(SO4)3 + 6H2O.
Which mixture yields a pH > 7?
Na2CO3 (basic) in excess over H2SO4 produces a basic solution (pH > 7).
In which reaction is H2O2 a reducing agent?
H2O2 reduces PbO2 to Pb²⁺ by losing electrons, acting as a reducing agent.
For 2Fe³⁺ + 2I⁻ → 2Fe²⁺ + I2, which is true?
I⁻ → I2 + 2e⁻ (oxidation). Fe³⁺ is reduced to Fe²⁺.
An element with multiple structural forms but the same chemical properties exhibits
Allotropy refers to different structural forms of an element, like carbon (diamond, graphite).
Sulphur
Sulphur burns with a blue flame, producing SO2. Its oxides are acidic, it is not spontaneously flammable, and it is non-conductive.
HNO3 is prepared in the lab by
NaNO3 + H2SO4 → HNO3 + NaHSO4 is the standard laboratory preparation of nitric acid.
Lime water, used to detect CO2, is
Lime water is a solution of Ca(OH)2, which reacts with CO2 to form CaCO3, causing milkiness.
Which is not true of CO?
CO does not oxidize to CO2 at room temperature; it requires high temperature or a catalyst.
ZnO + Na2O → Na2ZnO2 and ZnO + CO2 → ZnCO3 show ZnO is
ZnO reacts with both a base (Na2O) and an acid (CO2), indicating amphoteric behavior.
In 3Cl2 + 2NH3 → N2 + 6HCl, NH3 acts as
NH3 reduces Cl2 to HCl by losing electrons, acting as a reducing agent.
In the Haber process, finely divided iron is
Iron catalyzes the reaction N2 + 3H2 ⇌ 2NH3, lowering the activation energy.
An organic compound (vapour density 56.5) has C=53.1%, H=6.2%, N=12.4%, O=28.3%. Its molecular formula is [C=12, H=1, N=14, O=16]
Molar mass = 2 × 56.5 = 113. Ratios: C = 53.1/12 ≈ 4.43, H = 6.2/1 = 6.2, N = 12.4/14 ≈ 0.89, O = 28.3/16 ≈ 1.77. Divide by 0.89: C5H7O2N. Molar mass = 113.
The hybridization of carbon in ethyne (C2H2) is
Ethyne’s triple bond involves sp-hybridized carbons, forming a linear structure.
Heating kerosene to obtain lower boiling liquids is
Cracking breaks large hydrocarbons into smaller, lower-boiling fractions like petrol.
Which compound is used in the Contact Process for H2SO4 production?
V2O5 catalyzes the oxidation of SO2 to SO3 in the Contact Process.
The oxidation number of nitrogen in NH4NO3 is
In NH4⁺: N + 4(+1) = +1, N = -3. In NO3⁻: N + 3(-2) = -1, N = +5.
Which is a primary alcohol?
Primary alcohols have the -OH group on a carbon bonded to one other carbon. CH3CH2OH (ethanol) is primary.
The trend in ionization energy across Period 3 is
Ionization energy increases across Period 3 due to increasing nuclear charge and decreasing atomic radius.
What is the pH of a 0.01 M NaOH solution? [Kw = 10⁻¹⁴]
[OH⁻] = 0.01 M. [H⁺] = 10⁻¹⁴ / 0.01 = 10⁻¹². pH = -log(10⁻¹²) = 12.
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