Praxis Chemistry 5245 case studies
Praxis Chemistry 5245 · Put your knowledge to work in context.
Praxis Chemistry (5245) is a subject-area content test used by many states and educator-preparation programs as one piece of the licensure process for prospective secondary chemistry teachers. It is intended for candidates who have completed or are completing a chemistry or science education program and need to demonstrate content knowledge before entering the classroom. The Praxis Chemistry 5245 case studies are 5 cases and about 3,009 words.
1Calorimetry Quandary: Heat Loss in a Coffee-Cup Calorimeter
A student dissolves 4.00 g of ammonium nitrate (molar mass 80.04 g/mol) in 50.0 g of water in a coffee-cup calorimeter. The initial temperature of the water is 22.4 °C and the final temperature after dissolution is 14.8 °C.
649 words, about 3 min2Le Chatelier in an Industrial Ammonia Reactor
A simplified Haber-Bosch reactor runs N2(g) + 3 H2(g) ⇌ 2 NH3(g), ΔH = −92 kJ/mol. The plant currently operates at 450 °C and 200 atm with a catalyst, achieving about 15% conversion per pass.
645 words, about 3 min3Why Does the Salt Water Bulb Stay Lit? Conductivity and Bonding
Students build a conductivity tester: a battery, a small bulb, and two graphite electrodes. They test four liquids: distilled water (bulb dim/off), 0.1 M NaCl(aq) (bulb bright), 0.1 M glucose(aq) (bulb off), and glacial acetic acid (bulb dim).
570 words, about 3 min4Titration Trouble: A Flat Buffer Region
A student titrates 25.0 mL of an unknown weak monoprotic acid with 0.100 M NaOH, monitoring pH. The curve shows an initial pH of 2.9, a gradual rise, a buffer region, an equivalence point near pH 8.7 at 20.0 mL of NaOH, and a final plateau.
572 words, about 3 min5Lab Safety and Inquiry Design: The Unexpected Precipitate
In an inquiry lab, students mix 0.1 M solutions of Pb(NO3)2 and KI and observe a yellow precipitate (PbI2). A student wants to determine how temperature affects the amount of precipitate and proposes heating the mixture to boiling, filtering hot, and weighing the dried solid.
573 words, about 3 min