Concentrated nitric acid is 70% HNO₃. The amount of concentrated nitric acid solution that should be used to prepare 250 mL of 2.0 M HNO₃ would be:

1. 45.0 g conc. HNO₃

2. 90.0 g conc. HNO₃

3. 70.0 g conc. HNO₃

4. 54.0 g conc. HNO₃

The mole fraction of the solute in a 1.00 molal aqueous solution is: 

6.02x10²⁰ molecules of urea are present in 100mL of its solution. The concentration of the solution is:

Which of The following has a maximum number of molecules?

1. 7g N₂ 

2. 2g H₂ 

3. 16g NO₂ 

4. 16g O₂ 

The number of moles of KMnO₄ reduced by one mole of KI in an alkaline medium is- 

1. One fifth 

2. Five

3. One

4. Two

The number of moles of oxygen in 1L of air containing 21% oxygen by volume, under standard conditions, is 

1. 0.0093 mole

2. 2.10 moles

3. 0.186 mole

4. 0.21 mole

What volume of  oxygen gas (O₂) measured at $0°\mathrm{C}$ and 1 atm, is needed to burn completely 1L of  propane gas (C₃H₈) measured under the same conditions?

1. 7L 

2. 6L

3. 5L

4. 10L

1 g of magnesium is burnt with 0.56g of oxygen in a closed vessel. The left-out reactant and its quantity are

(At. weight of Mg = 24, O=16)

1. Mg, 0.16g

2. O₂, 0.16g

3. Mg, 0.44g

4. O₂, 0.28g

Percentage of Se in peroxidase anhydrase enzyme is 0.5% by weight (at. weight = 78.4), then minimum molecular weight of peroxidase anhydrase enzyme is

1. 1.568 x 10³ 

2. 15.68

3. 2.168 x 10⁴ 

4. 1.568 x 10⁴ 

Number of moles of Mn${\mathrm{O}}_4^{-}$ required to oxidise one mole of ferrous oxalate completely in acidic medium will be 

1. 0.6 mole

2. 0.4 mole

3. 7.5 moles

4. 0.2 mole