Chemistry Class XI - Moleconcept -1

A gas mixture contains N2 and O2 with mole fractions of 0.7 and 0.3 respectively. If the total pressure is 1 atm, calculate the partial pressure of O2.

• 0.3 atm

• 0.7 atm

• 1 atm

• 0.4 atm

A reaction vessel contains a mixture of H2, O2, and N2 in a mole ratio of 2:1:3 at 1 atm pressure. If the temperature of the mixture is increased, how does it affect the partial pressure of each gas, assuming ideal behavior and constant volume?

• Increases for all gases

• Decreases for all gases

• Increases for H2 and O2, decreases for N2

• Remains the same for all gases

Consider an experiment where the density of a substance is measured. Three different instruments provide the following data: Instrument A (high precision, low accuracy): 2.35 g/mL, 2.36 g/mL, 2.35 g/mL Instrument B (low precision, high accuracy): 2.30 g/mL, 2.50 g/mL, 2.45 g/mL Instrument C (high precision, high accuracy): 2.40 g/mL, 2.41 g/mL, 2.40 g/mL Which instrument is most reliable for scientific experiments?

• Instrument A

• Instrument B

• Instrument C

• None of the instruments

For the reaction MnO–4 + 8H+ + 5e– → Mn2+ + 4H2O, calculate the n-factor for MnO–4.

• 1

• 5

• 8

• 4

What is the formula mass of CaCl2?

• 111 g/mol

• 40 g/mol

• 71 g/mol

• 95 g/mol

A 2.0 M solution of H2SO4 is mixed with a 1.0 M solution of NaOH. Calculate the pH of the resultant solution, assuming complete neutralization and a final volume of 1 L.

• 1

• 7

• 0

• Cannot be determined from the given information

A hydrated salt X·nH2O loses 36% of its weight on heating. If the molar mass of X is 160 g/mol, determine n.

• 3

• 5

• 6

• 10

The reaction between Na2CO3 and CaCl2 is represented as: Na2CO3 + CaCl2 → CaCO3 + 2NaCl If 106 g of Na2CO3 (molar mass = 106 g/mol) reacts with 111 g of CaCl2 (molar mass = 111 g/mol), which is the limiting reagent?

• Na2CO3

• CaCl2

• Neither, as they react completely

• Both, as the reaction is in perfect stoichiometric ratio

A gas mixture contains 40% O2 and 60% N2 by volume. Calculate the molar mass of the mixture.

• 28.8

• 29.6

• 30.4

• 32.0

In the reaction 2H2 + O2 → 2H2O, 4g of hydrogen reacts with excess oxygen. The reaction vessel has a leak that allows 2 g of water to escape. How much water remains in the vessel?

• 34 g

• 36 g

• 18 g

• 20 g