CLEP Chemistry case studies
CLEP Chemistry · Put your knowledge to work in context.
The CLEP Chemistry exam is a standardized, multiple-choice assessment that lets students earn college credit by demonstrating knowledge equivalent to a one-year general chemistry course. It is intended for self-directed learners-incoming college students, adult learners, and military personnel-who have already acquired the material through prior coursework, independent study, or laboratory experience and want to accelerate their degree without retaking introductory chemistry. The CLEP Chemistry case studies are 5 cases and about 2,522 words.
1Identifying an Unknown Carbonate by Back-Titration
A student receives a 2.500 g sample of an unknown Group 2 metal carbonate, MCO3, contaminated with inert NaCl. The student dissolves the sample in 50.00 mL of 1.000 M HCl, boils off the CO2, then titrates the excess acid with 0.5000 M NaOH, requiring 28.40 mL to reach the endpoint.
421 words, about 2 min2Le Chatelier Reasoning in a Sealed NO2/N2O4 System
A rigid 2.00 L flask at 298 K is filled with a mixture of NO2 (brown) and N2O4 (colorless) that has reached equilibrium: N2O4(g) ⇌ 2NO2(g), Kc = 4.6 × 10⁻³ at 298 K. The equilibrium mixture is visibly pale brown.
519 words, about 3 min3Rate Data That Don't Fit a Simple Order
A kinetics team studies the reaction A + B → products at 300 K and collects initial-rate data in a sealed reactor: Trial [A]₀ (M) [B]₀ (M) Initial rate (M/s) --- --- --- --- 1 0.10 0.10 2.0 × 10⁻⁴ 2 0.20 0.10 8.0 × 10⁻⁴ 3 0.10 0.20 2.0 × 10⁻⁴ 4 0.10 0.10 2.0 × 10⁻⁴ (with 0.05 M added product P) A junior analyst concludes the reaction is second order in A and first order in B (overall third order) because 'doubling A quadruples the rate and B must matter too.' The team lead is skeptical of the B conclusion and of the analyst's proposed mechanism. Determine the rate law from Trials 1–3.
551 words, about 3 min4Choosing an Indicator and Buffering in a Weak-Acid Titration
A student titrates 25.00 mL of 0.100 M acetic acid (Ka = 1.8 × 10⁻⁵) with 0.100 M NaOH. The lab has three indicators: methyl orange (pH 3.1–4.4), bromothymol blue (pH 6.0–7.6), and phenolphthalein (pH 8.2–10.0).
473 words, about 2 min5Calorimetry, Sign Conventions, and a Suspicious ΔH
A student dissolves 4.00 g of NH4NO3 (molar mass 80.04 g/mol) in 96.0 g of water in a coffee-cup calorimeter (assume the solution's specific heat is 4.18 J/g·°C and the calorimeter heat capacity is negligible). The initial temperature is 22.5 °C; after stirring, the final temperature is 17.3 °C.
558 words, about 3 min