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Chemistry QUESTION #1447

Which compound will give a positive silver mirror test with Tollens' reagent?

Propanone
Ethanal✔️
Benzophenone
None of these

Correct Answer Logic:

Tollens' reagent ($[\text{Ag(NH}_3)_2]^+$) is a mild oxidising agent that distinguishes aldehydes from ketones. Aldehydes are oxidised to carboxylates and silver is reduced to metallic silver (the silver mirror). Ethanal ($CH_3CHO$) is an aldehyde → gives positive result. Propanone and benzophenone are ketones → do not react (ketones cannot be further oxidised under mild conditions).

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MCQs Section QUESTION #5256

Question 7842

شاعری میری ایجاد ہے یہ کس کا جملہ ہے؟

افضل حسین
الٰہی بخش
مرزا غالب✔️
ان میں سے کوئی نہیں

Correct Answer Logic:

یہ مشہور جملہ مرزا غالب کا ہے جو اپنی شاعری کی انفرادیت پر فخر کا اظہار کرتا ہے۔

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Psychology QUESTION #9843

Question 7843

The theory of personality in which 'basic anxiety' is the primary concept was associated with:

Fromm
Sullivan
Horney✔️
Murray

Correct Answer Logic:

Karen Horney placed basic anxiety — the pervasive feeling of being alone and helpless in a hostile world — at the centre of her theory. She proposed three neurotic coping strategies: moving toward, against, or away from people.

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English Literature QUESTION #702

Question 7844

In "1984," what is "Newspeak"?

A new dialect
A language to limit thought✔️
A universal language
None of these

Correct Answer Logic:

Newspeak is a controlled language designed by the state to diminish the range of thought.

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Psychology QUESTION #9723

Question 7845

In classical conditioning, the weakening and eventual disappearance of a conditioned response when the conditioned stimulus is repeatedly presented without the unconditioned stimulus is known as:

Spontaneous recovery
Generalization
Discrimination
Extinction✔️

Correct Answer Logic:

Extinction in classical conditioning occurs when the conditioned stimulus (CS) is repeatedly presented without the unconditioned stimulus (UCS), causing the conditioned response (CR) to gradually weaken and disappear. Importantly, extinction does not erase the original learning; spontaneous recovery (re-emergence of the CR after rest) demonstrates the original association is retained in memory.

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Security Measures to Maintain Law and Order QUESTION #954

Question 7846

What is the purpose of a 'Security Restricted Area' (SRA) pass?

It is a souvenir
To authorize specific individuals into sensitive zones✔️
To get discounts at airport shops
To show the person is an officer

Correct Answer Logic:

Pass systems ensure that only vetted and authorized personnel have access to areas critical to aviation safety.

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Chemistry QUESTION #1083

Question 7847

The standard heat of formation of Ba$^{2+}$(aq) in kcal/mol is: [Given: $\Delta H_f^\circ(\text{SO}_4^{2-}(\text{aq})) = -216\ \text{kcal/mol}$, $\Delta H_\text{cryst}(\text{BaSO}_4) = -4.5\ \text{kcal/mol}$, $\Delta H_f^\circ(\text{BaSO}_4(\text{s})) = -349\ \text{kcal/mol}$]

$+133.0$
$+220.5$
$-128.5$
$-133.0$✔️

Correct Answer Logic:

$\Delta H_f^\circ(\text{BaSO}_4,\text{s}) = \Delta H_f^\circ(\text{Ba}^{2+},\text{aq}) + \Delta H_f^\circ(\text{SO}_4^{2-},\text{aq}) + \Delta H_\text{cryst}$. $-349 = \Delta H_f^\circ(\text{Ba}^{2+}) + (-216) + (-4.5)$. $\Delta H_f^\circ(\text{Ba}^{2+}) = -349 + 216 + 4.5 = -128.5\ \text{kcal/mol}$. Wait: crystallisation is lattice formation from ions, so: $\Delta H_f^\circ(\text{BaSO}_4,\text{s}) = \Delta H_f^\circ(\text{Ba}^{2+}) + \Delta H_f^\circ(\text{SO}_4^{2-}) + \Delta H_\text{cryst}\Rightarrow \Delta H_f^\circ(\text{Ba}^{2+})=-349+216+4.5=-128.5$. Hmm, but options show -133.0. Using Hess's: $\Delta H_f^\circ(\text{Ba}^{2+})=-349-(-216)-(-4.5)=-349+216+4.5=-128.5$. Closest: option (3) = -128.5.

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Paper-I (Anatomy/Physiology and Biochemistry/Microbiology) QUESTION #3319

Question 7848

'Tetanus' is caused by an anaerobic bacterium called:

*Clostridium tetani*✔️
*Bacillus anthracis*
*Vibrio cholerae*
*Bordetella pertussis*

Correct Answer Logic:

It produces a potent neurotoxin that causes muscle stiffness (lockjaw).

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Math Physics Chemistry Biology QUESTION #11378

Question 7849

________ are spherical sacs surrounded by a single membrane containing hydrolytic enzymes:

Mitochondria
Body vesicles
Lysosomes✔️
Chloroplast

Correct Answer Logic:

Lysosomes are membrane-bound spherical sacs containing over 50 hydrolytic (digestive) enzymes including proteases, lipases, nucleases, and glycosidases. These enzymes function optimally at the acidic pH (~4.8) maintained inside the lysosome. They digest worn-out organelles, pathogens, and macromolecules.

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Agriculture Economics QUESTION #11862

Question 7850

Stage II of production, the economically rational stage, is defined by the range over which:

$MPP$ is negative
$MPP$ is above $APP$
$MPP$ is positive but below $APP$, and above zero✔️
$APP$ is rising

Correct Answer Logic:

Stage II runs from the point where $MPP = APP$ down to where $MPP = 0$ — output still rises but at a diminishing rate.

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Statistics QUESTION #1992

Question 7851

For a symmetric distribution, Bowley's coefficient of skewness is 0 and Pearson's coefficient $\beta_1 = \dfrac{\mu_3^2}{\mu_2^3}$ equals:

$1$
$0$✔️
$-1$
$3$

Correct Answer Logic:

For a perfectly symmetric distribution, the third central moment $\mu_3 = 0$ (since positive and negative deviations cancel symmetrically). Therefore $\beta_1 = \dfrac{\mu_3^2}{\mu_2^3} = \dfrac{0}{\mu_2^3} = 0$. Note: $\beta_1 = 0$ indicates zero skewness.

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General Knowledge QUESTION #8692

Question 7852

When was the People's Republic of China founded?

1947
1948
1949✔️
None of above

Correct Answer Logic:

Communist China was founded on October 1, 1949.

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Physics QUESTION #7225

Question 7853

What are the dimensions of the magnetic field $B$ in terms of $C$ (coulomb), $M$, $L$, and $T$?

$M^1L^1T^{-2}C$
$M^1L^0T^{-1}C^{-1}$✔️
$M^1L^0T^{-2}C$
$M^1L^1T^{-1}C$

Correct Answer Logic:

From the Lorentz force: $F = qvB$

$[B] = \dfrac{[F]}{[q][v]} = \dfrac{MLT^{-2}}{C \cdot LT^{-1}} = MT^{-1}C^{-1} = M^1L^0T^{-1}C^{-1}$

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Law QUESTION #9504

Question 7854

A sues B for damages arising from a road accident. A resides in Islamabad. The accident occurred in Peshawar. B resides in Lahore and carries on business in Quetta. A chooses to file the suit in the Lahore Civil Court. Can A validly institute the suit in Lahore?

Yes; under Section 19 CPC for a suit for compensation for wrong to the person, A may sue either where the wrong was done (Peshawar) or where B resides or carries on business (Lahore or Quetta); Lahore is a valid forum✔️
No; A must sue in Islamabad since A resides there
No; only Peshawar, where the accident occurred, is the proper forum
Yes; A can choose any Court in Pakistan

Correct Answer Logic:

Section 19 CPC provides that for suits for compensation for wrong to the person or moveable property, the plaintiff may institute the suit either where the wrong was done or where the defendant resides or carries on business. B resides in Lahore, making Lahore a valid forum at A's option.

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Boilers Mechanical Engineering QUESTION #2418

Question 7855

Newton's Law of Cooling for convection heat transfer gives the heat flux $q''_{conv}$ as:

$q''_{conv} = k(T_w - T_\infty)/L$
$q''_{conv} = h(T_w - T_\infty)$ where $h$ is the convection coefficient (W/m²·K)✔️
$q''_{conv} = \sigma\varepsilon T_w^4$
$q''_{conv} = \rho c_p (T_w - T_\infty)$

Correct Answer Logic:

Newton's Law of Cooling: $q''_{conv}=h(T_w-T_\infty)$, where $h$ (W/m²·K) is the convection heat transfer coefficient.

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Boilers Mechanical Engineering QUESTION #2469

Question 7856

The wear load $F_w$ on a gear tooth (Buckingham equation) depends on which key gear geometry parameter related to the smaller gear?

$F_w \propto r_g^2$ (gear pitch radius squared)
$F_w = d_p B K Q$ where $d_p$ is the PINION pitch diameter✔️
$F_w \propto N_p/N_g$ (tooth ratio)
$F_w \propto P_d^2$ (diametral pitch squared)

Correct Answer Logic:

Buckingham's wear load: $F_w=d_p B K Q$, where $d_p$ is the pinion pitch diameter, $B$ is face width, $K$ is the stress-fatigue factor, and $Q=2N_g/(N_p+N_g)$ is the ratio factor.

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Physics QUESTION #1023

Question 7857

An electric dipole with dipole moment $5 \times 10^{-6}\ \text{Cm}$ is aligned with a uniform electric field of magnitude $4 \times 10^5\ \text{N/C}$. The dipole is rotated through $60°$. The change in potential energy is:

1.2 J
1.5 J
0.8 J
1.0 J✔️

Correct Answer Logic:

Initial PE: $U_i = -pE\cos0° = -pE$. Final PE: $U_f = -pE\cos60° = -\frac{pE}{2}$. Change: $\Delta U = U_f - U_i = -\frac{pE}{2}+pE = \frac{pE}{2} = \frac{5\times10^{-6}\times4\times10^5}{2} = \frac{2}{2} = 1.0\ \text{J}$.

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Mathematics QUESTION #4116

Question 7858

Let $W$ be the subspace of all symmetric $2 \times 2$ matrices. What is $\dim(W)$?

$2$
$3$✔️
$4$
$6$

Correct Answer Logic:

Symmetric $2 \times 2$ matrices have form $\begin{pmatrix} a & b \ b & c \end{pmatrix}$. Basis: $\begin{pmatrix} 1 & 0 \ 0 & 0 \end{pmatrix}$, $\begin{pmatrix} 0 & 1 \ 1 & 0 \end{pmatrix}$, $\begin{pmatrix} 0 & 0 \ 0 & 1 \end{pmatrix}$. Dimension is 3.

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