#### 131. A chemist has 3.5 moles of NaCl, 2.4 moles of KCl, and 4.1 moles of MgCl2. She needs to prepare a solution and uses 1.2 moles of NaCl, 0.8 moles of KCl, and 1.5 moles of MgCl2. How many moles of each compound are left in the container?
["### How Chemists Calculate Remaining Moles: A Step-by-Step Breakdown of NaCl, KCl, and MgCl₂ Usage", "When preparing chemical solutions, precise stoichiometric calculations are essential. Understanding how much of each reactant remains after use helps ensure accurate experiments and prevents waste. This article examines a practical scenario involving three common inorganic salts: NaCl (sodium chloride), KCl (potassium chloride), and MgCl₂ (magnesium chloride), guiding readers through the calculation of remaining moles after a solution is prepared.", "---", "### The Situation: Initial Moles and Usage", "The chemist begins with the following amounts:", "- NaCl: 3.5 moles\n- KCl: 2.4 moles\n- MgCl₂: 4.1 moles", "She then removes specific quantities for her solution:", "- 1.2 moles of NaCl\n- 0.8 moles of KCl\n- 1.5 moles of MgCl₂", "---", "### Step 1: Calculate Remaining Moles After Usage", "To find how many moles remain, subtract the amount used from the initial quantity for each compound.", "#### For NaCl:\n[ 3.5 \ ext{ moles} - 1.2 \ ext{ moles} = 2.3 \ ext{ moles of NaCl remaining} ]", "#### For KCl:\n[ 2.4 \ ext{ moles} - 0.8 \ ext{ moles} = 1.6 \ ext{ moles of KCl remaining} ]", "#### For MgCl₂:\n[ 4.1 \ ext{ moles} - 1.5 \ ext{ moles} = 2.6 \ ext{ moles of MgCl₂ remaining} ]", "---", "### Why These Calculations Matter in Chemistry", "Accurate molar accounting ensures:", "- Proper solution concentration\n- Reproducibility of experiments\n- Safe and efficient reagent use", "Molar excesses prevent under- or over-preparation, while deficit checks indicate precision and reliability in analytical work.", "---", "### Summary of Remaining Compounds", "| Compound | Initial Moles | Moles Used | Moles Remaining |\n|----------|---------------|------------|------------------|\n| NaCl | 3.5 | 1.2 | 2.3 moles |\n| KCl | 2.4 | 0.8 | 1.6 moles |\n| MgCl₂ | 4.1 | 1.5 | 2.6 moles |", "---", "### Conclusion", "Mastering mole calculations is foundational for chemists. This example demonstrates how simple subtraction based on usage provides clear insight into reactant availability. Always track starting amounts and consumption carefully to maintain precision in lab work — a cornerstone of successful scientific practice.", "---", "Keywords: NaCl moles remaining, KCl remaining after usage, MgCl₂ calculation, stoichiometric remainder, chemistry lab calculations, mole reduction, solution preparation, chemistry education, chemical inventory management", "---", "Need more guidance on stoichiometry or laboratory calculations? Stay tuned — we’ll break down common challenges and applications every chemist faces."]
