ACT Science Practice Question #1314 (Medium (30)) | Test Citadel
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ACT Science Difficulty: Medium (30)

Digital ACT Science Practice Question #1314

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A chemistry student must prepare a $0.2\text{ M}$ aqueous solution of potassium chloride (KCl) starting from a stock solution with concentration $2.5\text{ M}$. The student measures exactly $40\text{ mL}$ of the $2.5\text{ M}$ stock solution. According to the dilution formula $M_1 V_1 = M_2 V_2$, what volume of distilled water, in milliliters, must be added to achieve the desired concentration?
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Socratic AI Engine Step-by-Step Derivation
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⚡ 15-Second Desmos Speed Hack

Read carefully: 'What volume of water must be ADDED?' Always subtract initial volume: $V_2 - V_1 = {v2} - {v1} = {water_needed}$.

Masterclass Solution & Distractor Trap Analysis

Using $M_1 V_1 = M_2 V_2$: $$(2.5\text{ M})(40\text{ mL}) = (0.2\text{ M})(V_2) \implies 100.0 = 0.2 V_2 \implies V_2 = \frac{100.0}{0.2} = 500\text{ mL}.$$ The question asks for the volume of water *added*, which is the final total volume ...

Distractor Analysis: Trap choice eliminates careless test-takers who confuse roots with coordinates...

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