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Chemistry QUESTION #7533

Hydrogen peroxide oxidizes $[\text{Fe(CN)}_6]^{4-}$ to $[\text{Fe(CN)}_6]^{3-}$ in acidic medium, and reduces $[\text{Fe(CN)}_6]^{3-}$ to $[\text{Fe(CN)}_6]^{4-}$ in alkaline medium. What are the other products formed in these two reactions, respectively?

H$_2$O and (H$_2$O + O$_2$)
H$_2$O and (H$_2$O + OH$^-$)
(H$_2$O + O$_2$) and H$_2$O✔️
(H$_2$O + O$_2$) and (H$_2$O + OH$^-$)

Correct Answer Logic:

Acidic medium (oxidising agent):
$[\text{Fe(CN)}_6]^{4-} + H_2O_2 + 2H^+ \to [\text{Fe(CN)}_6]^{3-} + \text{H}_2\text{O}$
H$_2$O$_2$ is reduced to H$_2$O. Other product: H$_2$O.

Alkaline medium (reducing agent):
$H_2O_2 \to H_2O + \frac{1}{2}O_2$ (H$_2$O$_2$ is oxidized)
$2[\text{Fe(CN)}_6]^{3-} + H_2O_2 + 2OH^- \to 2[\text{Fe(CN)}_6]^{4-} + O_2 + 2H_2O$
Other products: H$_2$O and O$_2$.

So the pair is: H$_2$O (acidic) and (H$_2$O + O$_2$) (alkaline).

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Chemistry QUESTION #7526

Question 1862

For the reaction $2\text{C}_{57}\text{H}_{110}\text{O}_6(s) + 163\ \text{O}_2(g) \to 114\ \text{CO}_2(g) + 110\ \text{H}_2\text{O}(l)$, find the mass of water produced from 445 g of C$_{57}$H$_{110}$O$_6$.

490 g
445 g
495 g✔️
890 g

Correct Answer Logic:

Molar mass of C$_{57}$H$_{110}$O$_6$: $57(12)+110(1)+6(16)=684+110+96=890\ \text{g mol}^{-1}$

Moles of C$_{57}$H$_{110}$O$_6 = \dfrac{445}{890} = 0.5\ \text{mol}$

From stoichiometry: 2 mol fat → 110 mol H$_2$O

So 0.5 mol fat → $\dfrac{110 \times 0.5}{2} = 27.5\ \text{mol H}_2\text{O}$

Mass of H$_2$O $= 27.5 \times 18 = \mathbf{495\ \text{g}}$

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Paper-I (Anatomy/Physiology and Biochemistry/Microbiology) QUESTION #3257

Question 1863

'Active Hyperemia' refers to increased blood flow to an organ due to:

A blockage
Increased metabolic activity (like exercise)✔️
Gravity
Sleep

Correct Answer Logic:

Local metabolites cause vasodilation to bring more blood to working muscles.

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Mathematics QUESTION #1323

Question 1864

The radius of curvature $\rho$ of the ellipse $\dfrac{x^2}{a^2}+\dfrac{y^2}{b^2}=1$ at the end of the minor axis $(0,b)$ is:

$\dfrac{b^2}{a}$
$\dfrac{a^2}{b}$✔️
$\dfrac{a}{b}$
$\dfrac{b}{a}$

Correct Answer Logic:

The radius of curvature of an ellipse at $(0,b)$ (end of minor axis): using the formula $\rho=\dfrac{(a^2\sin^2t+b^2\cos^2t)^{3/2}}{ab}$ at $t=\pi/2$: $\rho=\dfrac{(a^2)^{3/2}}{ab}=\dfrac{a^3}{ab}=\dfrac{a^2}{b}$.

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Physics QUESTION #7090

Question 1865

A particle moves in a circular orbit under a central force $F \propto R^{-n}$. If the period is $T$, then:

$T \propto R^{(n+1)/2}$✔️
$T \propto R^{n/2}$
$T \propto R^{3/2}$
$T \propto R^{\frac{n}{2}+1}$

Correct Answer Logic:

Centripetal force $F = \frac{mv^2}{R} \propto \frac{1}{R^n}$.

$v^2 \propto \frac{1}{R^{n-1}} \implies v \propto R^{(1-n)/2}$
$T = \frac{2\pi R}{v} \propto \frac{R}{R^{(1-n)/2}} = R^{1 - (\frac{1-n}{2})} = R^{(n+1)/2}$.

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Economics QUESTION #1706

Question 1866

Despite numerous social protection programmes, Pakistan continues to face deep-rooted poverty. Which structural challenge has proven most intractable in the country's poverty reduction efforts?

Establishing equitable access to productive resources — land, credit, and education — across income groups✔️
Expanding the outreach and loan size of microfinance institutions
Narrowing persistent spatial disparities between rapidly growing urban centres and lagging rural areas
None of these

Correct Answer Logic:

The most fundamental and intractable challenge in Pakistan's poverty alleviation agenda has been ensuring equitable access to productive resources: highly skewed land distribution (top 1% own disproportionate land), limited access to formal credit for smallholders and women, and unequal quality of education across socioeconomic groups perpetuate intergenerational poverty. Microcredit and urban-rural parity are related but secondary policy levers.

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Chemistry QUESTION #7143

Question 1867

A specific compound with the formula $A_{2}B_{3}$ crystallizes in an HCP lattice. Determine which atom constitutes the lattice and the fraction of tetrahedral voids occupied by the other atom.

Lattice: A; $\frac{2}{3}$ of Tetrahedral voids occupied by B
Lattice: A; $\frac{1}{3}$ of Tetrahedral voids occupied by B
Lattice: B; $\frac{2}{3}$ of Tetrahedral voids occupied by A
Lattice: B; $\frac{1}{3}$ of Tetrahedral voids occupied by A✔️

Correct Answer Logic:

In an HCP lattice, if there are $n$ atoms of B, the number of tetrahedral voids is $2n$. In the formula $A_2B_3$, the ratio of $A:B$ is $2:3$, which can be written as $\frac{2}{3}:1$. If B forms the lattice ($n$ atoms), then A occupies $2/3$ atoms. The fraction of tetrahedral voids occupied by A is $\frac{\text{atoms of A}}{\text{total tetrahedral voids}} = \frac{2/3}{2} = \frac{1}{3}$.

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Mathematics QUESTION #4087

Question 1868

The number of distinct cyclic subgroups of $\mathbb{Z}_{18}$ is equal to the number of positive divisors of 18. How many such subgroups exist?

$4$
$5$
$6$✔️
$8$

Correct Answer Logic:

Divisors of $18 = 2 \times 3^2$ are: $1,2,3,6,9,18$ — exactly 6 divisors. By the subgroup theorem for cyclic groups, $\mathbb{Z}_{18}$ has exactly one cyclic subgroup of each order dividing 18, giving $6$ cyclic subgroups in total.

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Home Economics QUESTION #6277

Question 1869

What is the chemical name for the natural polymer found in Cotton and Linen?

Fibroin
Polyester
Cellulose✔️
Keratin

Correct Answer Logic:

Cellulose is the complex carbohydrate that forms the main structural component of plant cell walls.

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Paper-I (Anatomy/Physiology and Biochemistry/Microbiology) QUESTION #3213

Question 1870

'Growth Hormone' (GH) is secreted by the:

Posterior Pituitary
Anterior Pituitary✔️
Thyroid Gland
Adrenal Medulla

Correct Answer Logic:

The anterior pituitary (adenohypophysis) produces GH, TSH, ACTH, etc.

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Paper-II (Pharmacognosy and Pharmaceutics-I) QUESTION #3657

Question 1871

A drug that kills or expels intestinal worms is called an:

Antipyretic
Anthelmintic✔️
Analgesic
Antiemetic

Correct Answer Logic:

Drugs like Santonin are anthelmintics.

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Medicinal Chemistry and Biopharmaceutics QUESTION #3816

Question 1872

Wool fat is unavailable and must be replaced by lanolin ($28\%$ water, $72\%$ wool fat). What amounts of lanolin and water are needed for the prescription: zinc oxide $2$ g, calamine $2$ g, wool fat $36$ g, water to $60$ g?

$34$ g lanolin and $22$ mL water
$40$ g lanolin and $16$ mL water
$46$ g lanolin and $10$ mL water
$50$ g lanolin and $6$ mL water✔️

Correct Answer Logic:

Lanolin needed $= \dfrac{36}{0.72} = 50$ g. Water from lanolin $= 50 \times 0.28 = 14$ mL. Total water in formula $= 60 - 2 - 2 - 36 = 20$ mL. Additional water $= 20 - 14 = 6$ mL.

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Urdu QUESTION #5037

Question 1873

'یہ سب تمہارا کرم ہے آقا' والی نعت کس نے لکھی ہے؟

اقبال عظیم
خالد محمود نقشبندی
مظفر وارثی✔️
ان میں سے کوئی نہیں

Correct Answer Logic:

یہ مشہور نعت 'یہ سب تمہارا کرم ہے آقا' مظفر وارثی نے لکھی ہے۔

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Law QUESTION #5659

Question 1874

When a criminal act is done by several persons in furtherance of the __________ of all each such person is liable for that act in the same manner as if it were done by him alone.

common intention✔️
common object
Mens Rea
Actus Rea

Correct Answer Logic:

Under Section 34 PPC when a criminal act is done by several persons in furtherance of the common intention of all each such person is liable for that act as if it were done by him alone. This is the doctrine of joint liability based on common intention.

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Economics QUESTION #1686

Question 1875

According to Keynes's liquidity preference theory, the relationship between the money supply and the rate of interest is best characterised as:

Negative — a higher money supply leads to a lower interest rate✔️
Positive — a higher money supply leads to a higher interest rate
Indirect — the relationship is mediated through the price level
No systematic relationship exists between the two

Correct Answer Logic:

In Keynes's Liquidity Preference Theory, the interest rate is determined by the supply of and demand for money. Given a fixed money demand curve, an increase in money supply shifts the supply curve rightward, lowering the equilibrium interest rate. The relationship is therefore negative (inverse): $\uparrow M_s \Rightarrow \downarrow r$. This is the mechanism through which monetary policy affects investment and aggregate demand in the Keynesian framework.

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Paper-I (Anatomy/Physiology and Biochemistry/Microbiology) QUESTION #3281

Question 1876

The protein coat that surrounds the viral nucleic acid is called the:

Envelope
Capsid✔️
Capsomere
Peplomer

Correct Answer Logic:

The capsid protects the viral genome from environmental damage.

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Egnlish QUESTION #691

Question 1877

"Transcendentalism" emphasizes the importance of:

Tradition
Reason over intuition
Individual intuition✔️
None of these

Correct Answer Logic:

Figures like Emerson believed that individuals have divine intuition and should rely on themselves rather than social institutions.

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Boilers Mechanical Engineering QUESTION #2511

Question 1878

According to the Gerber (parabolic) fatigue criterion, the equation relating $\sigma_a$, $\sigma_m$, $S_e$, and $S_{ut}$ is:

$\frac{\sigma_a}{S_e} + \frac{\sigma_m}{S_{ut}} = 1$
$\left(\frac{n\sigma_a}{S_e}\right) + \left(\frac{n\sigma_m}{S_{ut}}\right)^2 = 1$
$\frac{\sigma_a}{S_e} + \left(\frac{\sigma_m}{S_{ut}}\right)^2 = 1$✔️
$\frac{\sigma_a}{S_e} \cdot \frac{\sigma_m}{S_{ut}} = 1$

Correct Answer Logic:

The Gerber parabolic criterion: $\frac{\sigma_a}{S_e}+\left(\frac{\sigma_m}{S_{ut}}\right)^2=1$. Gerber's curve passes through the central region of fatigue failure data.

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