10 g of MgCO₃ decomposes on heating to 0.1 mole CO₂ and 4 g MgO. The percent purity of MgCO₃ is

• 24%

• 44%

• 84%

• 74%

The compound Na₂CO₃ . x H₂O has 50% H₂O by mass. The value of "x" is

• 4

• 5

• 6

• 8

The volume of oxygen liberated at STP from 15 mL of 20 volume H₂O₂ is

• 100 mL

• 200 mL

• 300 mL

• 400 mL

Calculate the molality of a solution that contains 51.2 g of naphthalene (C₁₀H₈) in 500 mL of carbon tetrachloride. The density of CCl₄ is 1.60 g/mL

• 0.250 m

• 0.500 m

• 0.750 m

• 0.840 m

When 2.46 gm of a hydrated salt (MSO₄xH₂O) is completely dehydrated, 1.20 gm of anhydrous salt is obtained. If the molecular weight of anhydrous salt is 120 gm mol^-1, what is the value of x?

• 2

• 7

• 4

• 6

326.

An organic compound contains 90% carbon and 10% hydrogen by mass. Its empirical formula is

• C₂H₄

• C₃H₆

• C₃H₈

• C₃H₄

The volume of neon gas in cm³ at STP having the same number of atoms as that present in 800 mg of Ca is (At. mass : Ca = 40 g mol^-1, Ne = 20 g mol^-1)

• 448

• 896

• 224

• 112

How many molecules of CO₂ are formed when one milligram of 100% pure CaCO₃ is treated with excess hydrochloric acid?

• 6.023 × 10²³

• 6.023 × 10¹⁸

• 6.023 × 10²¹

• 6.023 × 10²²

5.0 g of sodium hydroxide (molar mass 40 g mol^-1) is dissolved in little quantity of water and the solution is diluted upto 100 ml. What is the molarity of the resulting solution?

• 0.1 mol dm^-3

• 1.0 mol dm^-3

• 0.125 mol dm^-3

• 1.25 dm^-3

The mole fraction of methanol is in 4.5 molal aqueous solution is

• 0.250

• 0.125

• 0.100

• 0.075