Question

How many molecules of H₂S are required to form 79.0 g of sulfur according to the following reaction? Assume excess SO2.

2 H₂S(g) + SO2(g) → 3 S(s) + 2H₂O(1)

Answer 1

9.89 x 10²³ molecules H₂S

Step-by-step explanation:

To find the molecules of H₂S, you need to (1) convert grams S to moles S (via the atomic mass of sulfur), then (2) convert moles S to moles H₂S (via the mole-to-mole ratio from equation coefficients), and then (3) convert moles H₂S to molecules H₂S (via Avogadro's Number). It is important to arrange the ratios/conversions in a way that allows for the cancellation of units. The final answer should have 3 sig figs to match the sig figs of the given value.

Atomic Mass (S): 32.065 g/mol

2 H₂S(s) + SO₂(g) -----> 3 S(s) + 2 H₂O(l)

Avogadro's Number:

6.022 x 10²³ molecules = 1 mole

79.0 g S 1 mole 2 moles H₂S 6.022 x 10²³ molecules
--------------- x --------------- x ---------------------- x ------------------------------------- =
32.065 g 3 moles S 1 mole

= 9.89 x 10²³ molecules H₂S