CHM MIDTERM EXAM QUESTIONS AND CORRECT ANSWERS |ALL GRADED A+

Ace your CHM Midterm Exam with this comprehensive question-and-answer study guide based on hands-on laboratory experiments. Perfect for general chemistry students preparing for midterms that cover experimental data analysis, reaction types, and stoichiometric calculations. This resource includes complete solutions covering: Experiment 1 – Unknown Solid Identification – solubility testing (not soluble, slightly soluble, very soluble), density calculation (mass/volume), water displacement (9.5 mL), melting point (71.0°C), identifying unknown solids (BHT, calcium carbonate), extensive vs. intensive properties (melting point = intensive, height = extensive) Experiment 1 – Synthesis Reaction (Magnesium + Oxygen) – mass change before/after heating (increase by 3.291 g), product identification (MgO), mole calculation (n = m/MM = 0.206 moles), balanced equation (2Mg + O₂ → 2MgO), empirical formula determination (CuO from copper oxide experiment) Experiment 2 – Unknown Liquid Identification – density calculation (0.869 g/mL), boiling point (108.0°C), identifying unknowns (cyclopentylamine matches density and boiling point) Experiment 2 – Decomposition Reaction (Copper Carbonate Hydroxide) – mass decrease (1.403 g lost), color change (green → black), product identification (CuO), mole calculation (0.0452 moles CuO), water vapor release calculation (0.8146 g H₂O), CO₂ gas release Experiment 2 – Copper(II) Sulfate Pentahydrate – color before heating (blue), NaOH addition (blue precipitate = copper hydroxide), mole calculation (0.1001 moles), empirical formula Experiment 3 – Single-Displacement Reaction (Zinc + HCl) – observation (bubbles), temperature and pressure increase (exothermic reaction), gas volume produced (73.6 mL), pressure decrease upon cooling (ideal gas law: P ∝ T) Experiment 4 – Double-Displacement Reaction (NiCl₂ + NaOH) – precipitate formation (green nickel hydroxide), balanced equation (2NaOH + NiCl₂ → 2NaCl + Ni(OH)₂), yellow precipitate identification Stoichiometry & Limiting Reactants (CuSO₄ + Na₂S) – precipitate mass varying with volumes (0.010g – 0.029g), maximum precipitate at 1:1 ratio (3 mL + 3 mL), excess reactant identification via supernatant testing (blue solution = excess CuSO₄, precipitate = excess Na₂S), 1:1 molar ratio determination Flame Tests – element flame colors (magnesium = white-gray, potassium nitrate = purple, lead nitrate = blue, strontium = red, zinc = gray-green, arsenic acid = light blue), electron excitation and ground state emission Mixture Separation – sublimation of NH₄Cl (mass = 0.529g, 5.29%), SiO₂ mass percent (66.45%), NaCl mass percent (28.26%), indirect calculation method Lithium Nitride Synthesis – empirical formula determination from mass data (Li₃N) Perfect for general chemistry midterm prep, lab practical exams, and stoichiometry review.