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Question 10.15: How many equivalents are in 3.1 g of the diprotic acid H2S? ...

How many equivalents are in 3.1 g of the diprotic acid H_2S? The molar mass of H_2S is 34.0 g.
ANALYSIS The number of acid or base equivalents is calculated by doing a gram to mole conversion using molar mass as the conversion factor and then multiplying by the number of H^+ ions produced.
BALLPARK ESTIMATE The 3.1 g is a little less than 0.10 mol of H_2S. Since it is a diprotic acid, (two H^+ per mole), this represents a little less than 0.2 Eq of H_2S.

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(3.1  \cancel{g  H_2S}) \left(\frac{1  \cancel{mol  H_2S}}{34.0  \cancel{g  H_2S}} \right) \left(\frac{2  Eq  H_2S}{ 1  \cancel{mol  H_2S}} \right) = 0.18  Eq  H_2S

BALLPARK CHECK The calculated value of 0.18 is consistent with our prediction of a little less than 0.2 Eq of H_2S.

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