Chemistry
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- The number of molecules in 4.4 g of CO2 is Answer: A. 6.022×10²² n=4.4/44=0.1 mol ⇒0.1×6.022×10²³ molecules. 1
- A compound contains 40% C, 6.67% H and 53.3% O by mass. Its empirical formula is Answer: D. CH2O Mole ratio C : H : O =40/12:6.67/1:53.3/16=3.33:6.67:3.33=1:2:1 . 1
- Under identical conditions, the ratio of the rates of effusion of H2 and O2 is Answer: B. 4 : 1 Graham's law: fracr_(H_2)r_(O_2)=√(32/2)=4 . 1
- The numbers of σ and π bonds in acrylonitrile (CH2=CH–C≡N) are Answer: C. 6 σ and 3 π σ: 3 C–H + 1 (C=C) + 1 (C–C) + 1 (C≡N) = 6. π: 1 (C=C) + 2 (C≡N) = 3. 1
- Ozonolysis of but-2-ene followed by treatment with Zn/H2O gives Answer: A. two molecules of ethanal CH₃CH=CHCH₃ is cleaved at the C=C bond to give 2 CH₃CHO. 1
- The number of radial nodes in a 3p orbital is Answer: B. 1 Radial nodes =n-l-1=3-1-1=1 . 1
- The maximum number of electrons in an atom that can have \(n=3\) and \(m_s=+\frac12\) is Answer: B. 9 The n=3 shell has n²=9 orbitals, and each holds one electron with m_s=+1/2 . 1
- The bond order of the superoxide ion O2− is Answer: D. 1.5 O₂⁻ has 17 electrons: bonding 10, antibonding 7. Bond order =10-7/2=1.5 . 1
- The shape of the ClF3 molecule is Answer: B. T-shaped Cl has 3 bond pairs and 2 lone pairs (sp³d). The lone pairs occupy equatorial positions, giving a T-shape. 1
- The oxidation number of oxygen in OF2 is Answer: A. +2 F is always −1: x+2(-1)=0⇒ x=+2 . 1
- Explain how pressure of a dry gas can be calculated using aqueous tension. i. When a gas is collected over water in a closed container, it gets mixed with the saturated water vapour in that space. Therefore, the mea... 1
- A gas at 772 mm Hg and at 35 °C occupies a volume of 6.851 L. Calculate its volume at STP. Given: V₁ = Initial volume = 6.851 L P₁ = Initial pressure = 772 mm Hg, P₂ = Final pressure = 760 mm Hg T₁ = Initial temperature = 35 °C = 3... 1
- Find the temperature in °C at which volume and pressure of 1 mol of nitrogen gas becomes 10 dm3 and 2.46 P = 2.46 atm, V = 10 dm³, n = 1 mol, R = 0.0821 dm³-atm K⁻¹ mol⁻¹ To find: Temperature (T) Formula: PV = nRT According to ideal gas equation... 1
- Calculate the temperature of 5.0 mol of a gas occupying 5 dm3 at 3.32 bar. (R = 0.083 bar dm3 K-1 mol-1) Given: n = number of moles = 5.0 mol, V = volume = 5 dm³ P = pressure = 3.32 bar, R = 0.083 bar dm³ K⁻¹ mol⁻¹ To find: Temperature (T) Formu... 1
- Calculate the number of moles of hydrogen gas present in a 0.5 dm3 sample of hydrogen gas at a pressure Given: V = 0.5 dm³ = 0.5 × 10⁻³ m³, P = 101.325 kPa = 101.325 × 10³ Pa = 101.325 × 10³ Nm⁻² T = 27 °C = 27 + 273.15 K = 300.15 K, R = 8.314... 1
- What is an ideal gas? The gases which obey’ ideal gas equation over a complete range of temperature and pressure are called ideal gases. For an ideal gas, the rat... 1
- What are real gases? Gases, which do not obey ideal gas equation under all the conditions of temperature and pressure are called real gases. For real gases, the... 1
- Explain the reason for deviations of gases from ideal behaviour. A deviation from the ideal behaviour is observed at high pressure and low temperature. It is due to two reasons. The intermolecular attracti... 1
- Explain: Liquefaction of CO2 with the help of pressure vs volume isotherm. Answer: Andrews' P–V isotherms of CO₂ show that CO₂ can be liquefied by pressure only below its critical temperature, 30.98 °C; at this temp... 1
- Define: Critical temperature, critical volume and critical pressure. i. The temperature above which a substance cannot be liquified by increasing pressure is called its critical temperature (T_c). ii. The mola... 1
- Water has Tc = 647.1 K and Pc = 220.6 bar. What do these values imply about the state of water under ordinary conditions The T_c and P_c values of water are very high compared to the room temperature and common atmospheric pressure. As a result, water exists in... 1
- Gases possess characteristic critical temperature which depends upon the magnitude of intermolecular forces When cooling of ammonia and carbon dioxide gas is started from 500 K, then ammonia reaches its critical temperature first (i.e., 405.5 K.) a... 1
- CO2 has Tc = 38.98 °C and Pc = 73 atm. How many phases of CO2 coexist at i. 50 °C and 73 atm ii. 20 °C and 50 atm. i. 50 °C and 73 atm represent a condition for CO₂ above its T_c. Therefore, under this condition CO₂ exists only as single phase. ii. 20° C... 1
- In which of the following cases, water will have the highest and the lowest boiling point? Higher the pressure to which a liquid is exposed, higher will be its boiling point. The pressure to which water is exposed is maximum in the... 1