Mole

The relative formula mass of a chloride, XCl, is 58.5. The relative atomic mass of X is .

• 11

• 17

• 23

• 35

What is the number of moles of hydrogen atoms in 1.7 g of ammonia gas (NH₃)?

• 0.1

• 0.3

• 1.4

• 1.7

Which of the following gases occupies 12 dm³ at room temperature and pressure?

• 4 g of helium

• 16 g of oxygen

• 20 g of neon

• 44 g of carbon dioxide

How many oxygen molecules are there in 64 g of oxygen gas?

• 3 × 10²³

• 6 × 10²³

• 1.2 × 10²⁴

• 2.4 × 10²⁴

256 g of sulfur vapour occupies the same volume as 2 g of hydrogen gas at room temperature and pressure. What is the formula of the sulfur molecule?

• S

• S₂

• S₄

• S₈

Which of the following gases weighs the most at room temperature and pressure?

• 0.5 dm³ of argon (Ar)

• 200 cm³ of ammonia (NH₃)

• 5 dm³ of hydrogen (H₂)

• 1000 cm³ of water vapour (H₂O)

Which of the following statements about the mole is not true?

• The mole is a unit of measurement for very small particles.

• A mole of any gas occupies 24 dm³ at room temperature and pressure.

• Equal volumes of any gas have the same mass.

• The mass of one mole of a compound is equal to its M_r in grams.

260 g of hydrated cobalt(II) chloride contains 118 g of water of crystallisation. What is the molecular formula of the compound?

• CoCl₂.2H₂O

• CoCl₂.3H₂O

• CoCl₂.6H₂O

• CoCl₂.12H₂O

0.8 g of sodium hydroxide is dissolved to form a 250 cm³ aqueous solution. What is the concentration of this solution?

• 0.02 mol/dm³

• 0.04 mol/dm³

• 0.08 mol/dm³

• 0.80 mol/dm³

Washing soda is hydrated sodium carbonate, Na₂CO₃.10H₂O (M_r = 286). Which of the following gives the percentage of water in washing soda?

• (106x100)/286

• (286x10x100)/106

• (10x18x100)/106

• (10x18x100)/286