261.

How many grams of the concentrated nitric solution should be used to prepare 250 mL o 2.0M HNO₃ ? The concentrated acid is 70% HNO₃.

• 45.0 g conc. HNO₃

• 90.0 g conc. HNO₃

• 70.0 g conc. HNO₃

• 70.0 g conc. HNO₃

6.02 x 10²⁰ molecules of urea are present in 100 mL of its solution. The concentration of solution is

• 0.02 M

• 0.01 M

• 0.001 M

• 0.001 M

Mole fraction of the solute in a 1.00 molal aqueous solution is 

• 0.0177

• 0.0344

• 1.7700

• 1.7700

Which one of the following statements is not true?

• Concentration of DO below 6 ppm is good for the growth of fish

• Clean water would have a BOD value of less than 5 ppm

• Oxides of sulphur, nitrogen and carbon are the most widespread air pollutant

• Oxides of sulphur, nitrogen and carbon are the most widespread air pollutant

If Avogadro number N_A, changed from 6.022 x 10²³ mol^-1 this would change

• the definition of mass in units of grams

• the mass of one mole of carbon

• the ratio of chemical species to each other in the balanced equation

• the ratio of chemical species to each other in the balanced equation

20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample? (Atomic weight of Mg =24)

• 75

• 96

• 60

• 60

What is the mass of precipitate formed when 50 mL of 16.9% solution of AgNO₃ is mixed with 50 mL of 5.8% NaCl solution?

(Ag = 107.8, N = 14, O = 16, Na = 23, Cl = 35.5)

• 28 g

• 3.5 g 

• 7 g 

• 7 g 

What is the mole fraction of the solute in a 1.00 m aqueous solution? 

• 0.177

• 1.770

• 0.0354

• 0.0354

The number of water molecules is maximum in 

• 18 molecules of water

• 1.8 g of water

• 18 g of water

• 18 g of water

Which has the maximum number of molecules among the following?

• 44 g CO₂

• 48 g O₃

• 8 g H₂

• 8 g H₂