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AIIMS B.Sc. Nursing practice questions

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Question 1Physics

In the physics of alveolar surfactant and liquid films, surface tension is defined as force per unit length acting along the surface. What is the SI unit of surface tension?

  1. newton metre
  2. newton per metre Correct answer.
  3. newton per square metre
  4. kilogram per metre second

Explanation

Surface tension is force divided by length, so its SI unit is newton per metre (N/m). The same quantity can be written as energy per unit area, joule per square metre, which reduces to N/m, but no such option is offered here. Newton per square metre is the unit of pressure, not of surface tension.

Question 2Physics

A patient's wheelchair starts from rest and accelerates uniformly at 2 m/s² along a straight hospital corridor. What distance does it cover in the first 5 s?

  1. 5 m
  2. 25 m Correct answer.
  3. 10 m
  4. 50 m

Explanation

For uniform acceleration from rest, distance is s = ½at². Substituting a = 2 m/s² and t = 5 s gives s = ½ × 2 × 25 = 25 m. Using the velocity after 5 s (10 m/s) gives a speed, not a distance, so it does not answer the question.

Question 3Physics

A therapeutic ultrasound unit used in physiotherapy emits waves of frequency 50 kHz. What is the time period of these waves?

  1. 20 microseconds Correct answer.
  2. 5 microseconds
  3. 50 microseconds
  4. 2 microseconds

Explanation

Time period is the reciprocal of frequency, T = 1/f. With f = 50 kHz = 50,000 Hz, T = 1/50,000 s = 2 × 10⁻⁵ s, which equals 20 microseconds. The numerical value of the frequency in kilohertz must not be confused with the period.

Question 4Physics

The plastic used for a spectacle lens has a refractive index of 1.5 with respect to air. Taking the speed of light in air as 3.0 × 10⁸ m/s, what is the speed of light inside the lens?

  1. 2.0 × 10⁸ m/s Correct answer.
  2. 3.0 × 10⁸ m/s
  3. 1.5 × 10⁸ m/s
  4. 4.5 × 10⁸ m/s

Explanation

Refractive index is the ratio of the speed of light in vacuum (or air, to good approximation) to that in the medium, n = c/v. Rearranging gives v = c/n = 3.0 × 10⁸ / 1.5 = 2.0 × 10⁸ m/s. Light must slow down in an optically denser medium, so any value above 3.0 × 10⁸ m/s is impossible.

Question 5Physics

An ideal heat engine in a hospital incinerator plant works between a source at 500 K and a sink at 300 K. What is its maximum possible efficiency?

  1. 20%
  2. 40% Correct answer.
  3. 67%
  4. 60%

Explanation

The Carnot efficiency sets the upper limit: η = 1 − T_cold/T_hot, with temperatures in kelvin. Here η = 1 − 300/500 = 0.40, that is 40%. Kelvin must be used, but because the ratio is dimensionless the same numerical result follows from the given values.

Question 6Physics

In a laboratory model of blood rising in a capillary, a liquid rises to height h in a tube of radius r. If the same liquid is used in a tube of radius r/2, the capillary rise becomes:

  1. 4h
  2. h
  3. h/2
  4. 2h Correct answer.

Explanation

Jurin's law gives the capillary rise as h = 2T cosθ/(ρgr), so height is inversely proportional to tube radius. Halving the radius therefore doubles the height, giving 2h. The 1/r dependence is linear, not squared, because radius appears to the first power only.

Question 7Physics

In the circuit of a medical monitoring device, a 6 Ω resistor and a 3 Ω resistor are connected in parallel. What is the equivalent resistance of this combination?

  1. 9 Ω
  2. 2 Ω Correct answer.
  3. 1.5 Ω
  4. 4.5 Ω

Explanation

For a parallel combination, 1/R = 1/R₁ + 1/R₂ = 1/6 + 1/3 = 1/2, so R = 2 Ω. The equivalent resistance of a parallel network is always smaller than the smallest individual resistor, which rules out 9 Ω and 4.5 Ω immediately.

Question 8Physics

A proton moves with speed v at an angle of 30° to a uniform magnetic field of strength B. What is the magnitude of the magnetic force acting on the proton?

  1. 2qvB
  2. qvB/2 Correct answer.
  3. qvB
  4. zero

Explanation

The magnetic force on a moving charge is F = qvB sinθ, where θ is the angle between velocity and field. Since sin 30° = 0.5, the force is qvB/2. The force is maximum only when the velocity is perpendicular to the field, and zero only when it is parallel.

Question 9Physics

A metal used as a photocathode in a light detector has a work function of 2.0 eV. Photons of energy 3.1 eV strike the metal. What is the maximum kinetic energy of the emitted photoelectrons?

  1. 2.0 eV
  2. 1.1 eV Correct answer.
  3. 5.1 eV
  4. 0 eV

Explanation

Einstein's photoelectric equation gives K_max = photon energy − work function. Subtracting, K_max = 3.1 eV − 2.0 eV = 1.1 eV. Emission is possible because the photon energy exceeds the work function, so the kinetic energy cannot be zero.

Question 10Physics

A satellite is in a circular orbit just above the Earth's surface. What is the ratio of its orbital speed to the escape speed from the Earth's surface?

  1. 1/√2 Correct answer.
  2. 2
  3. √2
  4. 1/2

Explanation

Orbital speed near the surface is v_o = √(GM/R), while escape speed is v_e = √(2GM/R). Dividing gives v_o/v_e = 1/√2, approximately 0.71. The ratio is less than one because escape requires more energy than merely staying in a low orbit.

Question 11Physics

A column of intravenous fluid exerts a pressure that is recorded in pascals (Pa). Expressed in SI base units, 1 Pa is equal to:

  1. kg m⁻¹ s⁻¹
  2. kg m s⁻²
  3. kg m⁻² s⁻²
  4. kg m⁻¹ s⁻² Correct answer.

Explanation

Pressure is force divided by area, so its base units come from dividing the base units of force (kg m s⁻²) by m². This gives kg m⁻¹ s⁻², which is the pascal. The newton, kg m s⁻², is the unit of force rather than pressure.

Question 12Physics

A patient's axillary temperature is charted as 37.0 °C. For use in a gas-law calculation, this temperature must be converted to the absolute scale. The value is:

  1. 273 K
  2. 236 K
  3. 310 K Correct answer.
  4. 300 K

Explanation

The Kelvin scale is obtained by adding 273 to the Celsius reading, so 37.0 + 273 ≈ 310 K. The conversion is a shift of the zero point, not a multiplication, and the degree size stays the same.

Question 13Physics

A ward attendant raises a 60 kg patient from floor level to a bed 0.80 m high, moving at constant speed. Taking g = 10 m/s², the work done against gravity is:

  1. 48 J
  2. 480 J Correct answer.
  3. 600 J
  4. 4800 J

Explanation

The work done against gravity equals the gain in gravitational potential energy, mgh = 60 × 10 × 0.80 = 480 J. Because the patient moves at constant speed there is no change in kinetic energy to add.

Question 14Physics

In an optics practical, an object is placed 30 cm from a convex lens of focal length 20 cm. The image is formed at a distance of:

  1. 12 cm
  2. 60 cm Correct answer.
  3. 50 cm
  4. 20 cm

Explanation

Using 1/f = 1/v − 1/u with f = +20 cm and u = −30 cm gives 1/v = 1/20 − 1/30 = 1/60, so v = +60 cm. The positive sign means a real image on the far side of the lens.

Question 15Physics

A vial supplied to a nuclear medicine department contains a radionuclide of half-life 6 hours with an activity of 800 MBq. If it is kept for 18 hours, the activity remaining will be:

  1. 100 MBq Correct answer.
  2. 267 MBq
  3. 200 MBq
  4. 400 MBq

Explanation

Eighteen hours is three half-lives, so the activity falls by a factor of 2³ = 8. Dividing 800 MBq by 8 leaves 100 MBq, since radioactive decay is exponential rather than linear.

Question 16Physics

An infusion set uses a narrow tube of radius r. If the tube is replaced by one of radius r/2, with the same length and the same pressure difference maintained, Poiseuille's law predicts that the volume flow rate becomes:

  1. one-half of the original value
  2. one-quarter of the original value
  3. one-sixteenth of the original value Correct answer.
  4. one-eighth of the original value

Explanation

Poiseuille's law gives flow rate proportional to the fourth power of the radius when length, viscosity and pressure difference are fixed. Halving the radius multiplies the flow by (1/2)⁴ = 1/16, a much larger fall than the change in cross-section alone would suggest.

Question 17Physics

In a diagnostic ultrasound examination, a pulse reflected from a tissue interface returns to the transducer 0.10 ms after emission. Taking the speed of ultrasound in soft tissue as 1540 m/s, the depth of the interface is about:

  1. 15.4 cm
  2. 3.9 cm
  3. 30.8 cm
  4. 7.7 cm Correct answer.

Explanation

The pulse travels to the interface and back, so the total path is 1540 × 0.10 × 10⁻³ = 0.154 m. The depth is half of this round trip, giving about 0.077 m or 7.7 cm.

Question 18Physics

A simple pendulum used in a teaching demonstration has period T. If the string length is increased to four times its original value while the amplitude is kept small, the new period is:

  1. T/4
  2. 2T Correct answer.
  3. 4T
  4. T/2

Explanation

For small oscillations the period of a simple pendulum is T = 2π√(L/g), so it varies as the square root of the length. Quadrupling L multiplies the period by √4 = 2.

Question 19Physics

A radiography unit operates at a tube voltage of 40 kV. Taking hc = 1.24 × 10⁻⁶ eV·m, the shortest wavelength present in the emitted X-ray spectrum is approximately:

  1. 7.8 × 10⁻¹² m
  2. 1.24 × 10⁻¹⁰ m
  3. 3.1 × 10⁻⁸ m
  4. 3.1 × 10⁻¹¹ m Correct answer.

Explanation

The cut-off wavelength is set by the entire kinetic energy of an electron being converted into one photon: λmin = hc/eV. Substituting V = 4.0 × 10⁴ V gives 1.24 × 10⁻⁶ / 4.0 × 10⁴ = 3.1 × 10⁻¹¹ m.

Question 20Physics

A centrifuge rotor of radius 10 cm spins a blood sample at 3000 revolutions per minute. Taking π² ≈ 10, the centripetal acceleration of the sample is about:

  1. 1.0 × 10³ m/s²
  2. 1.0 × 10⁴ m/s² Correct answer.
  3. 1.0 × 10⁵ m/s²
  4. 3.1 × 10³ m/s²

Explanation

The frequency is 3000/60 = 50 rev/s, so ω = 2πf and ω² = 4π²f² ≈ 4 × 10 × 2500 = 1.0 × 10⁵ s⁻². Then a = ω²r = 1.0 × 10⁵ × 0.10 = 1.0 × 10⁴ m/s², which is roughly a thousand times g.

Question 21Physics

Which quantity used in nursing biomechanics is a vector and therefore requires both magnitude and direction for a complete description?

  1. Body temperature
  2. Displacement of a limb Correct answer.
  3. Blood pressure
  4. Total body water volume

Explanation

Displacement is a vector because a change in position has both magnitude and direction. Temperature, pressure, and volume are scalars, described completely by magnitude with an appropriate unit.

Question 22Physics

A portable suction pump connected to a 12 V battery draws a current of 2.5 A. What electrical power does the pump consume?

  1. 30 W Correct answer.
  2. 9.6 W
  3. 0.21 W
  4. 4.8 W

Explanation

Electrical power is the product of voltage and current, so P = VI = 12 V × 2.5 A = 30 W. This is the rate at which the pump transfers electrical energy.

Question 23Physics

A 20 kg hospital trolley is pushed along a corridor at a steady speed of 1.5 m/s. What is the kinetic energy of the trolley?

  1. 15 J
  2. 22.5 J Correct answer.
  3. 30 J
  4. 45 J

Explanation

Kinetic energy is given by KE = ½mv². Substituting m = 20 kg and v = 1.5 m/s gives ½ × 20 × 2.25 = 22.5 J.

Question 24Physics

A dressing pack is accidentally released from rest at a height of 1.8 m above the floor. Taking g = 10 m/s² and ignoring air resistance, how long does it take to reach the floor?

  1. 0.3 s
  2. 0.6 s Correct answer.
  3. 0.9 s
  4. 1.2 s

Explanation

For free fall from rest, h = ½gt², so t = √(2h/g). Here t = √(2 × 1.8 / 10) = √0.36 = 0.6 s.

Question 25Physics

An ice pack contains 0.50 kg of ice at 0 °C. How much heat is required to melt it completely into water at 0 °C? The specific latent heat of fusion of ice is 3.34 × 10⁵ J/kg.

  1. 1.67 × 10⁴ J
  2. 6.68 × 10⁵ J
  3. 3.34 × 10⁵ J
  4. 1.67 × 10⁵ J Correct answer.

Explanation

At the melting point, the heat needed is Q = mL, where L is the specific latent heat of fusion. Thus Q = 0.50 kg × 3.34 × 10⁵ J/kg = 1.67 × 10⁵ J.

Question 26Physics

In a nebulizer, air moves rapidly through a narrow jet and more slowly through the wider chamber. Compared with the wider chamber, the air pressure at the narrow jet is

  1. lower Correct answer.
  2. the same
  3. zero
  4. higher

Explanation

For steady horizontal flow, Bernoulli's principle relates pressure to speed: where the speed is greater, the pressure is lower. The narrow jet therefore has a lower pressure than the wider chamber.

Question 27Physics

The sound intensity level measured in a hospital ward is 60 dB. Taking the reference intensity as 1.0 × 10⁻¹² W/m², what is the sound intensity in the ward?

  1. 1.0 × 10⁻¹² W/m²
  2. 1.0 × 10⁻³ W/m²
  3. 1.0 × 10⁻⁹ W/m²
  4. 1.0 × 10⁻⁶ W/m² Correct answer.

Explanation

Sound intensity level is L = 10 log₁₀(I/I₀). A level of 60 dB means log₁₀(I/I₀) = 6, so I = 10⁶ × 1.0 × 10⁻¹² = 1.0 × 10⁻⁶ W/m².

Question 28Physics

A light beam inside a glass optical fibre of refractive index 1.5 approaches the glass–air boundary. What is the critical angle for total internal reflection at this boundary?

  1. 41.8° Correct answer.
  2. 48.6°
  3. 30.0°
  4. 56.3°

Explanation

The critical angle C satisfies sin C = n_air / n_glass = 1.0 / 1.5 = 0.667. Taking the inverse sine gives C ≈ 41.8°, above which total internal reflection occurs.

Question 29Physics

A uniform metre scale of weight 2 N is pivoted at its centre. A 4 N weight is hung 20 cm to the left of the pivot. Where must a 2 N weight be hung on the right side to balance the scale?

  1. 80 cm
  2. 40 cm Correct answer.
  3. 10 cm
  4. 20 cm

Explanation

The weight of the uniform scale acts at the pivot, so it produces no torque about the centre. Balancing moments gives 4 N × 0.20 m = 2 N × d, so d = 0.40 m, or 40 cm to the right.

Question 30Physics

The coefficient of viscosity of a fluid has the unit pascal-second (Pa·s). Expressed in SI base units, 1 Pa·s is equal to

  1. kg m⁻² s⁻¹
  2. kg m s⁻¹
  3. kg m⁻¹ s⁻²
  4. kg m⁻¹ s⁻¹ Correct answer.

Explanation

Since 1 Pa = 1 N/m² = 1 kg m⁻¹ s⁻², multiplying by one second gives 1 Pa·s = 1 kg m⁻¹ s⁻¹. This is the base-SI form of the viscosity unit.

Question 31Physics

During a transfusion, 0.50 kg of packed red cells is warmed from 20 °C to 37 °C. If the specific heat capacity of the fluid is 4200 J kg⁻¹ K⁻¹, how much heat is absorbed?

  1. 3.6 × 10⁴ J Correct answer.
  2. 1.8 × 10⁴ J
  3. 7.1 × 10⁴ J
  4. 1.4 × 10⁵ J

Explanation

The heat required is Q = mcΔT, where ΔT = 37 − 20 = 17 K. Substituting m = 0.50 kg and c = 4200 J kg⁻¹ K⁻¹ gives Q = 0.50 × 4200 × 17 = 3.57 × 10⁴ J, which rounds to 3.6 × 10⁴ J.

Question 32Physics

A bedside monitor draws a current of 0.50 A from a 6.0 V battery pack. What is the effective resistance of the monitor circuit?

  1. 12 Ω Correct answer.
  2. 3.0 Ω
  3. 24 Ω
  4. 6.0 Ω

Explanation

Ohm's law gives R = V/I. Substituting V = 6.0 V and I = 0.50 A gives R = 6.0/0.50 = 12 Ω.

Question 33Physics

In a defibrillator, the energy-storage component is rated in farads. The farad is the SI unit of which physical quantity?

  1. Electrical resistance
  2. Capacitance Correct answer.
  3. Electric potential difference
  4. Electric charge

Explanation

The farad (F) is defined as one coulomb per volt, which is the unit of capacitance. Charge is measured in coulombs, potential difference in volts and resistance in ohms.

Question 34Physics

In a capillary tube of internal radius 0.20 mm, water rises to a height h. Taking the surface tension of water as 0.072 N m⁻¹, the contact angle as 0°, density as 1000 kg m⁻³ and g = 10 m s⁻², what is h?

  1. 0.72 cm
  2. 14.4 cm
  3. 7.2 cm Correct answer.
  4. 3.6 cm

Explanation

Capillary rise is given by h = 2γ cosθ/(ρgr). With γ = 0.072 N m⁻¹, θ = 0°, ρ = 1000 kg m⁻³, g = 10 m s⁻² and r = 0.20 mm = 2.0 × 10⁻⁴ m, h = 0.144/(2.0) = 0.072 m = 7.2 cm.

Question 35Physics

A 100 μF capacitor in a defibrillator is charged to 2000 V. How much energy is stored?

  1. 20 J
  2. 400 J
  3. 200 J Correct answer.
  4. 2000 J

Explanation

For a capacitor, the energy stored is E = ½CV². With C = 100 μF = 1.0 × 10⁻⁴ F and V = 2000 V, E = 0.5 × 1.0 × 10⁻⁴ × (2000)² = 200 J.

Question 36Physics

A continuous-wave Doppler probe emits ultrasound at 2.0 MHz toward blood flowing directly toward the probe. The received frequency shift is 500 Hz. Taking the speed of sound in tissue as 1540 m s⁻¹, what is the blood speed?

  1. 0.77 m s⁻¹
  2. 0.096 m s⁻¹
  3. 0.19 m s⁻¹ Correct answer.
  4. 0.38 m s⁻¹

Explanation

For blood moving directly toward the probe, the Doppler shift is Δf = 2fv/c, where the factor 2 accounts for the transmitted and reflected paths. Rearranging gives v = Δf c/(2f) = 500 × 1540/(2 × 2.0 × 10⁶) ≈ 0.19 m s⁻¹.

Question 37Physics

A gamma source in a radiotherapy store produces a dose rate of 400 μSv h⁻¹. A lead sheet has a half-value layer of 0.50 mm for this radiation. What thickness of lead reduces the dose rate to 25 μSv h⁻¹?

  1. 4.0 mm
  2. 1.0 mm
  3. 2.0 mm Correct answer.
  4. 1.5 mm

Explanation

Each half-value layer reduces the dose rate by a factor of 2, so a reduction from 400 to 25 μSv h⁻¹ is a factor of 16, or 2⁴. Four half-value layers are therefore needed: 4 × 0.50 mm = 2.0 mm.

Question 38Physics

A platinum resistance thermometer has a resistance of 100.0 Ω at 0 °C and a temperature coefficient of resistance of 0.0039 °C⁻¹. What is its resistance at 50 °C, assuming a linear change?

  1. 100.0 Ω
  2. 105.0 Ω
  3. 119.5 Ω Correct answer.
  4. 110.0 Ω

Explanation

For a linear resistance thermometer, R = R₀(1 + αΔT). Substituting R₀ = 100.0 Ω, α = 0.0039 °C⁻¹ and ΔT = 50 °C gives R = 100.0(1 + 0.195) = 119.5 Ω.

Question 39Physics

At a soft-tissue–bone interface, the acoustic impedances are 1.6 × 10⁶ kg m⁻² s⁻¹ for soft tissue and 7.8 × 10⁶ kg m⁻² s⁻¹ for bone. For a pulse striking the interface at normal incidence, what fraction of the incident intensity is reflected?

  1. About 44% Correct answer.
  2. About 12%
  3. About 56%
  4. About 88%

Explanation

At normal incidence the intensity reflection coefficient is R = [(Z₂ − Z₁)/(Z₂ + Z₁)]². Substituting the impedances gives [(7.8 − 1.6)/(7.8 + 1.6)]² = (6.2/9.4)² ≈ 0.44, so about 44% is reflected.

Question 40Physics

An aerosol droplet of radius 0.10 mm and density 900 kg m⁻³ settles through air of viscosity 1.8 × 10⁻⁵ Pa s. Using Stokes' law and neglecting buoyancy, what is the terminal speed of the droplet? Take g = 10 m s⁻².

  1. 2.2 m s⁻¹
  2. 1.1 m s⁻¹ Correct answer.
  3. 11 m s⁻¹
  4. 0.11 m s⁻¹

Explanation

Stokes' law gives the terminal speed as v = 2r²(ρ − σ)g/(9η); neglecting buoyancy, v = 2r²ρg/(9η). With r = 1.0 × 10⁻⁴ m, ρ = 900 kg m⁻³, g = 10 m s⁻² and η = 1.8 × 10⁻⁵ Pa s, v = (2 × 1.0 × 10⁻⁸ × 900 × 10)/(9 × 1.8 × 10⁻⁵) ≈ 1.1 m s⁻¹.

Question 41Chemistry

In the quantum mechanical model of the atom, which set of quantum numbers is permissible for an electron in a 3d orbital?

  1. n = 3, l = 2, m_l = –1, m_s = +1/2 Correct answer.
  2. n = 3, l = 3, m_l = 0, m_s = –1/2
  3. n = 3, l = 2, m_l = –3, m_s = +1/2
  4. n = 2, l = 2, m_l = +1, m_s = +1/2

Explanation

For a 3d orbital the principal quantum number is n = 3 and the azimuthal quantum number is l = 2. The magnetic quantum number m_l can take values from −2 to +2, and m_s is either +1/2 or −1/2, so the set n = 3, l = 2, m_l = −1, m_s = +1/2 is allowed.

Question 42Chemistry

How many moles of oxygen atoms are present in 1.5 moles of aluminium sulfate, Al2(SO4)3?

  1. 18 mol Correct answer.
  2. 4.5 mol
  3. 6 mol
  4. 1.5 mol

Explanation

Each formula unit of Al2(SO4)3 contains three sulfate groups, and each sulfate group has four oxygen atoms, giving 12 oxygen atoms per formula unit. Therefore 1.5 mol of Al2(SO4)3 contains 1.5 × 12 = 18 mol of oxygen atoms.

Question 43Chemistry

According to VSEPR theory, the molecular shape of NH3 is best described as:

  1. trigonal planar geometry
  2. tetrahedral electron geometry
  3. trigonal pyramidal shape Correct answer.
  4. bent molecular shape

Explanation

NH3 has three N–H bond pairs and one lone pair on nitrogen, giving four electron domains and a tetrahedral electron geometry. The lone pair compresses the bond angles, so the observed molecular shape is trigonal pyramidal rather than tetrahedral.

Question 44Chemistry

A 0.10 m aqueous solution of glucose and a 0.10 m aqueous solution of sodium chloride are compared. Assuming complete dissociation of NaCl, which statement about their boiling points is correct?

  1. The boiling points cannot be compared without knowing solution volumes.
  2. Both solutions boil at the same temperature because their molalities are identical.
  3. The NaCl solution boils higher because it yields more particles per formula unit. Correct answer.
  4. The glucose solution boils higher because glucose forms more hydrogen bonds.

Explanation

Boiling point elevation is a colligative property that depends on the total molality of dissolved particles. NaCl dissociates into two ions per formula unit, so 0.10 m NaCl gives about 0.20 mol of particles per kg, whereas glucose gives 0.10 mol, hence NaCl boils higher.

Question 45Chemistry

For the exothermic reaction N2(g) + 3H2(g) ⇌ 2NH3(g), which change will increase the equilibrium yield of ammonia?

  1. Decreasing the total pressure
  2. Decreasing the temperature Correct answer.
  3. Adding a catalyst
  4. Increasing the temperature

Explanation

The reaction is exothermic, so lowering the temperature shifts the equilibrium in the direction that produces heat, namely toward NH3. A decrease in pressure would shift the equilibrium toward the side with more gas molecules, which is the reactant side, and a catalyst does not alter the equilibrium position.

Question 46Chemistry

In the electrochemical cell Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s), which statement is correct under standard conditions?

  1. Cu2+ ions are oxidized at the anode.
  2. Zn is the cathode and undergoes reduction.
  3. The standard cell potential is negative because zinc is more reactive than copper.
  4. Electrons flow from zinc to copper through the external circuit. Correct answer.

Explanation

Zinc has the more negative standard reduction potential, so it is oxidized at the anode and copper(II) is reduced at the cathode. Electrons therefore travel through the external circuit from zinc to copper, and the standard cell potential is positive: E°cell = 0.34 − (−0.76) = 1.10 V.

Question 47Chemistry

The IUPAC name of CH3–CH(OH)–CH2–CH2–CHO is:

  1. 2-hydroxypentanoic acid
  2. 2-hydroxypentanal
  3. 4-hydroxypentanoic acid
  4. 4-hydroxypentanal Correct answer.

Explanation

The aldehyde carbon is given number 1, so numbering the chain gives the hydroxyl group at carbon 4. The suffix for an aldehyde is -al, and the hydroxyl substituent is named as a prefix, giving 4-hydroxypentanal.

Question 48Chemistry

Which of the following statements about the primary structure of a protein is correct?

  1. It is maintained mainly by hydrogen bonds between backbone amide groups.
  2. It refers to the association of two or more polypeptide chains into a quaternary complex.
  3. It describes the folding of a single polypeptide chain into a three-dimensional shape.
  4. It is the linear sequence of amino acids joined by peptide bonds. Correct answer.

Explanation

Primary structure refers to the exact order of amino acids in a polypeptide chain, and these residues are linked by peptide bonds. Folding into helices or sheets is secondary structure, while overall three-dimensional folding is tertiary structure and multi-chain assembly is quaternary structure.

Question 49Chemistry

For a reaction at constant temperature and pressure, which combination of ΔH and ΔS always makes the reaction spontaneous?

  1. ΔH > 0 and ΔS > 0
  2. ΔH < 0 and ΔS > 0 Correct answer.
  3. ΔH < 0 and ΔS < 0
  4. ΔH > 0 and ΔS < 0

Explanation

The Gibbs free energy change is given by ΔG = ΔH − TΔS. When ΔH is negative and ΔS is positive, both contributions make ΔG negative at every temperature, so the process is spontaneous under all conditions.

Question 50Chemistry

Which of the following complexes is expected to be diamagnetic?

  1. [CoF6]3−
  2. [Fe(H2O)6]3+
  3. [Fe(CN)6]3−
  4. [Fe(CN)6]4− Correct answer.

Explanation

[Fe(CN)6]4− contains Fe2+, a d6 ion, and cyanide is a strong-field ligand that causes low-spin pairing of all six d electrons. With no unpaired electrons in the t2g set, the complex is diamagnetic. The other complexes have unpaired electrons and are paramagnetic.