Some Basic Concepts of Chemistry Previous Year Questions — NEET Chemistry

2 past-year Some Basic Concepts of Chemistry questions from NEET (Chemistry).

Q49 (2024)

When $1 \text{ dm}^3$ of $CO_2$ gas is passed over hot coke the volume of gaseous mixture after complete reaction at STP becomes $1.4 \text{ dm}^3$. The composition of the gaseous mixture at STP is:
  1. (1) $0.6 \text{ dm}^3$ of CO, $0.8 \text{ dm}^3$ of $CO_2$
  2. (2) $0.8 \text{ dm}^3$ of CO, $0.8 \text{ dm}^3$ of $CO_2$
  3. (3) $0.8 \text{ dm}^3$ of CO, $0.6 \text{ dm}^3$ of $CO_2$
  4. (4) $0.6 \text{ dm}^3$ of CO, $0.4 \text{ dm}^3$ of $CO_2$
### Related Formula $$CO_2(g) + C(s) \rightarrow 2CO(g)$$ ### Core Logic Initial volume of $CO_2 = 1 \text{ dm}^3$. At equilibrium: Volume of $CO_2 = 1 - x$ Volume of $CO = 2x$ Total volume = $(1 - x) + 2x = 1 + x = 1.4 \text{ dm}^3 \implies x = 0.4 \text{ dm}^3$. Volume of $CO_2 = 1 - 0.4 = 0.6 \text{ dm}^3$. Volume of $CO = 2(0.4) = 0.8 \text{ dm}^3$. ### Step 1: Final Selection Composition is $0.8 \text{ dm}^3$ of CO and $0.6 \text{ dm}^3$ of $CO_2$. ### Pattern Recognition 1 mole of $CO_2$ produces 2 moles of CO. Expansion in volume $\Delta V = x$. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Some Basic Concepts of Chemistry

Q65 (2024)

The number of hydrogen atoms present in 5.4 g of urea is: (Given: Molar mass of urea: $60 \text{ g mol}^{-1}$, $N_A = 6.022 \times 10^{23} \text{ particles mol}^{-1}$)
  1. (1) $2.168 \times 10^{23}$
  2. (2) $2.168 \times 10^{22}$
  3. (3) $1.084 \times 10^{22}$
  4. (4) $1.084 \times 10^{23}$
### Related Formula $$\text{Moles of urea} = \frac{w}{M} = \frac{5.4}{60} = 0.09 \text{ mol}$$ $$\text{Formula of Urea} = NH_2CONH_2 \implies 4 \text{ H atoms per molecule}$$ ### Core Logic $$\text{Number of H atoms} = 0.09 \times 4 \times 6.022 \times 10^{23} = 2.1679 \times 10^{23} \approx 2.168 \times 10^{23}$$ ### Step 1: Conclusion Number of hydrogen atoms is $2.168 \times 10^{23}$. ### Pattern Recognition Urea contains 4 hydrogen atoms per molecule: $N_H = 4 \times n_{urea} \times N_A$. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Some Basic Concepts of Chemistry
Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)

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