mole concept

A sample of methane (CH₄) has a volume of 12 dm³ at room temperature and pressure. Calculate the number of moles of CH₄ in the sample. (include units in your answer)

A hydrocarbon molecule C_xH_y has a relative molecular mass of 42. What are the values of x and y?

• x =1, y = 2

• x=3, y =6

• x=6, y=3

• x=6, y=6

What is the mass of one mole of aluminum?

• 26.981 g/mol

• 13 g/mol

• 53.985 g/mol

• 14 g/mol

A compound has the formula CH₃CO₂H.

How should the relative molecular mass, M_r, of this compound be calculated?

• 12 + 1 + 16

• 3(12 + 1) + 2(12 + 16) + 1

• (2 x 12) + (4 x 1) + (2 x 16)

• (4 x 12) + (2 x 1) + 16

Which of the following about 12 dm³ of nitrogen and 12 dm³ of carbon monoxide is correct?

 

1 Both contain 3 x 10²³ molecules.

2 Each contain 0.5 mole of gas.

3 Both have the same mass.

• 1 only

• 1 and 2

• 2 and 3

• All of the above

Relative atomic mass, A_r, is defined by comparing the mass of one atom with the mass of another atom, Z.

What is Z?

• ¹²C

• ¹H

• ²⁴Mg

• ¹⁶O

What is the molar mass of one molecule of Nitrogen N₂?

• 14 amu (atomic mass units)

• 14 g

• 28 g

• 28 amu

What is the molar mass of one mole of N₂ molecules ?

• 6.02 x 10²³ molecules

• 14.007 g

• 28.014 g

• 28.014 amu

Calculate the % composition by mass of oxygen present in H₂SO₄.

• 16.3%
• 65.25%
• 32.6%
• 57.14%

Carbon, ¹²₆C, and sulfur, ³²₁₆S, form the compound carbon disulfide, CS_2.

What is the relative molecular mass, M_r, of carbon disulfide?

• 6 + 16

• 6 + (2 x 16)

• 12 + 32

• 12 + (2 x 32)