Question

Calculate the number of atoms of carbon (C) in 463 cm³ of the colorless gas cyclobutane at 0 °C and atmospheric pressure, where its density is 2.50×10^-3 g cm^-3. The molecular formula of cyclobutane is C₄H₈.

Answer 1

Volume = 463 cm3 = 0.463 L (1cm3 = 0.001 L)

Molar mass of C4H8 = 4C + 8H = 4(12) + 8(1)

= 48+8 = 56 g/mol

Now, at STP (0°C, 1atm) :

22.4 L contain 1 mole C4H8 = 6.022×10²³ molecules

0.463 L contain 0.463×6.022×10²³/22.4 molecules

= 1.24×10²² molecules

1 molecule of C4H8 contain 4 C atoms

1.24×10²² molecule of C4H8 contain 4×1.24×10²² atoms

= 4.98×10²² C atoms