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Set and relations Question: Consider the relation R on the set {-2,-1,0,1,2} defined by (a,b) ∈ R if and only if 1+ ab > 0 . Then, among the statements : I. The number of elements in R is 17 II. R is an equivalence relation  A) only I is true  B) only II is true  C) Both I and II are true   D) Neither I nor II is true Your Answer: Check Answer Correct Answer: A) only I is true Solution: \(\) Difficulty: Medium Tags: Set and relations , Medium, JEE MATHS  Explore More 🧭

StudyBeacon Quiz – Mole Concept (JEE Main 2026 PYQ) Score: 0 Q1.  In the reaction: $2Al + 6HCl \rightarrow 2Al^{3+} + 6Cl^- + 3H_2$ 6.72 L H₂ at STP per mole Al 33.6 L H₂ regardless of T,P 12 L HCl consumed for 6 L H₂ 11.2 L H₂ at STP per mole HCl Check Answer From equation: $6$ mol HCl → $3$ mol H₂ $1$ mol HCl → $\frac{1}{2}$ mol H₂ At STP: $1$ mol gas = 22.4 L $\frac{1}{2} \times 22.4 = 11.2$ L Q2. Reaction: $CaCO_3 + 2HCl → CaCl_2 + H_2O + CO_2$ Given: 90 g $CaCO_3$, 300 mL HCl (38.55%, density 1.13 g/mL) 32.85 g CaCO₃ remains 97.30 g HCl reacted 64.97 g HCl remains 60.32 g HCl remains Check Answer Mass of solution = $300×1.13=339$ g Mass HCl = $0.3855×339=130.7$ g Moles HCl = $\frac{130.7}{36.5}=3.58$ mol Moles CaCO₃ = $\frac{90}{100}=0.9$ mol Needed HCl = $2×0.9=1.8$ mol Excess HCl remains → 64.97 g Q3. $A + 2B → AB_2$ 36 g A (60 g/mol), 56 g B (80 g/mol) A and B only C and D only B and D only A and C only ...

Modern Physics – JEE Main PYQs (2026) Quiz Important Constants: $h = 6.63 \times 10^{-34}\ \text{J·s}$ $c = 3 \times 10^8\ \text{m/s}$ $e = 1.6 \times 10^{-19}\ \text{C}$ $k = 1.38 \times 10^{-23}\ \text{J/K}$ $1\text{ eV} = 1.6 \times 10^{-19}\ \text{J}$ Score: 0 Q1. Two electrons are moving in orbits of two hydrogen-like atoms with speeds $3 \times 10^5$ m/s and $2.5 \times 10^5$ m/s respectively. If the radii of these orbits are nearly same then the possible order of energy states are respectively: 9 and 8 8 and 10 10 and 12 6 and 5 Check Answer For hydrogen-like atom: $v \propto \frac{1}{n}$ $\frac{v_1}{v_2} = \frac{n_2}{n_1}$ $\frac{3}{2.5} = 1.2$ Closest integer ratio → 9 and 8. Q2. Number of photons of equal energy emitted per second by a 6 mW laser source operating at 663 nm is: $1\times10^{16}$ $5\times10^{16}$ $2\times10^{16}$ $5\times10^{15}$ Check Answer $E = \frac{hc}{\lambda}$ $E = \frac{6.63\times10^{-34...