Physical Science: Chemistry — Midterm exam
Parent / teacher answer keyAn independent assessment of the core chapters listed below, followed by corrections and discussion.
18 questions · 42 points · suggested 60 minutes
Student instructions
- Suggested time: 60 minutes; allow breaks or accommodations and record them.
- Work independently with a calculator, blank paper and the reference relationships printed in this paper. Grades 9, 11 and 12 may also use the course-linked NYSED reference tables. Use no lesson notes or answer key during an assessed attempt.
- Show reasoning and units for written tasks. All supplied datasets are illustrative; do not present them as measurements you collected.
- Objective items: 1 point each. Written items: 3 points each, one per criterion. A parent or teacher marks the written work; the app never grades an explanation automatically.
- Sample exam: try the whole paper before opening the worked key, then revisit the linked chapters. The sample and final are different papers; this is a course assessment, not an official Regents examination.
Reference relationships
| Relationship, constant or reference | Use / conditions |
|---|---|
| Density | ρ=m/V; Mass and volume in consistent units |
| Amount | n=m/Mm; N=nNA; Mm is molar mass, not molarity |
| Concentration | M=n/V; M₁V₁=M₂V₂; Solution liters; dilution without reaction or loss |
| Ideal gas | PV=nRT; Kelvin and absolute pressure; R matched to units |
| Heating | q=mcΔT; qphase=mL; One phase versus phase change |
| Reaction heat | qreaction≈−qsurroundings; Include apparatus/loss terms when needed |
| Free energy | ΔG=ΔH−TΔS; Kelvin and matching energy units; not reaction rate |
| Equilibrium | Q, K=products/reactants with powers; Omit pure phases in the school approximation |
| Acidity | pH≈−log[H₃O⁺]; Concentration approximation; neutral near 7 at 25°C |
| Buffer | pH≈pKa+log([A⁻]/[HA]); Both conjugate species appreciable |
| Cell potential | E°cell=E°cathode−E°anode; Both table values are reduction potentials |
| Radioactive parent | N=N₀(½)^(t/thalf); Closed parent accounting; statistical model |
| NA=6.022×10²³ mol⁻¹ | Avogadro constant, rounded for school calculations |
| h=6.626×10⁻³⁴ J·s | Planck constant, rounded |
| c=3.00×10⁸ m/s | Vacuum light speed, rounded |
| e=1.602×10⁻¹⁹ C | Elementary charge magnitude; 1 eV=1.602×10⁻¹⁹ J |
| g=9.8 m/s² | Typical near-surface Earth approximation; use a supplied local value if given |
| R=8.314 J/(mol·K) | Use SI pressure Pa and volume m³ |
| R=0.0821 L·atm/(mol·K) | Use atmosphere pressure and liter volume |
| F≈96485 C/mol electrons | Faraday constant |
| 1 u·c²≈931.5 MeV | Mass-energy conversion for consistent nuclear mass accounting |
| T(K)=T(°C)+273.15 | Use 273 only when a question specifies that rounded convention |
| 1 L=1000 mL; 1 mL=1 cm³ | Volume conversions |
| 1 kWh=3.60×10⁶ J | Energy conversion |
| cwater≈4.18 J/(g·°C) | Approximate liquid-water specific heat in ordinary conditions |
| Lf,water≈334 J/g; Lv,water≈2260 J/g | Water fusion and vaporization near ordinary-pressure transition conditions |
| H | 1.008 g/mol |
| C | 12.01 g/mol |
| N | 14.01 g/mol |
| O | 16.00 g/mol |
| Na | 22.99 g/mol |
| Mg | 24.31 g/mol |
| Al | 26.98 g/mol |
| P | 30.97 g/mol |
| S | 32.06 g/mol |
| Cl | 35.45 g/mol |
| K | 39.10 g/mol |
| Ca | 40.08 g/mol |
| Fe | 55.85 g/mol |
| Cu | 63.55 g/mol |
| Zn | 65.38 g/mol |
| Ag | 107.87 g/mol |
| NH₄⁺ / OH⁻ / NO₃⁻ | Ammonium +1; hydroxide −1; nitrate −1 |
| CO₃²⁻ / SO₄²⁻ / PO₄³⁻ | Carbonate −2; sulfate −2; phosphate −3 |
Coverage and marks
| Chapter | Questions | Points |
|---|---|---|
| Investigating Matter | 1, 2, 3 | 7 |
| Atoms, Electrons & Periodicity | 4, 5, 6 | 7 |
| Bonding, Formulas & Molecular Structure | 7, 8, 9 | 7 |
| Reactions, Moles & Composition | 10, 11, 12 | 7 |
| Stoichiometry & Yield | 13, 14, 15 | 7 |
| States of Matter & Gases | 16, 17, 18 | 7 |
Name: ____________________ Date: ____________________
Question 1 · 1 point
A mixture contains 5 g salt and 8 g sand. After complete physical separation, what total dry solid mass should be recovered in a closed no-loss model?
Question 2 · 3 points
A sample has mass 24.0 g and volume 8.00 mL. Find density.
Question 3 · 3 points
Evaluate the evidence in this supplied classroom investigation: Density and Measurement Evidence. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Question 4 · 1 point
An atom of selenium has atomic number 34 and mass number 80. How many neutrons does it have?
Question 5 · 3 points
An atom is written in isotope notation with mass number 27 and atomic number 13 (aluminum). Find its numbers of protons, neutrons, and electrons.
Question 6 · 3 points
Evaluate the evidence in this supplied classroom investigation: Spectrum Evidence and Identification. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Question 7 · 1 point
Aluminum forms Al³⁺ and oxygen forms O²⁻. In the neutral compound aluminum oxide, how many oxide ions combine with every 2 aluminum ions?
Question 8 · 3 points
Predict the formula of the ionic compound formed between magnesium and chlorine.
Question 9 · 3 points
Evaluate the evidence in this supplied classroom investigation: Bond Models and Material Properties. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Question 10 · 1 point
Classify the reaction 2KClO₃ → 2KCl + 3O₂.
- synthesis
- decomposition
- single replacement
- double replacement
Question 11 · 3 points
Classify this reaction and explain your choice: 2Na + Cl₂ → 2NaCl.
Question 12 · 3 points
Evaluate the evidence in this supplied classroom investigation: Atom Accounting and Ionic Change. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Question 13 · 1 point
For N₂ + 3H₂ → 2NH₃, how many moles of ammonia form from 9.0 mol of hydrogen (with excess nitrogen)?
Question 14 · 3 points
For the reaction N₂ + 3H₂ → 2NH₃, how many moles of ammonia (NH₃) can be produced from 6.0 mol of hydrogen (H₂) reacting with excess nitrogen?
Question 15 · 3 points
Evaluate the evidence in this supplied classroom investigation: Limiting-Reactant Production Model. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Question 16 · 1 point
Convert 27°C to kelvin.
Question 17 · 3 points
A heating curve for a pure substance shows temperature rising, then holding flat at 80°C, then rising again, then holding flat at 218°C, then rising once more. Identify what is happening at each of the two flat plateaus.
Question 18 · 3 points
Evaluate the evidence in this supplied classroom investigation: Heating-Curve Energy Budget. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.