A container contains 255 g of a mixture of and . The mixture was treated with excess and 67.2 L of w — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question
Question
A container contains 255 g of a mixture of $Pt$ and $Zn$. The mixture was treated with excess $HCl$ and 67.2 L of $H_2$ was released at STP. The percentage of $Pt$ in the mixture is: (At. wt. $Pt=195, Zn=65$)
Answer: B
💡 Solution & Explanation
$Zn + 2HCl \rightarrow ZnCl_2 + H_2$. $Pt$ does not react. Moles $H_2 = 67.2 / 22.4 = 3 \text{ mol}$. Moles $Zn = 3 \text{ mol}$. Mass $Zn = 3 \times 65 = 195 \text{ g}$. Mass $Pt = 255 - 195 = 60 \text{ g}$. $\%Pt = (60/255) \times 100 \approx 23.5\%$.
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