Post-Lab Problems

In addition to the problem types already described, Chem21Labs can generate unique post-lab questions using . . . .

1. student data - any value shown on a student's page can be reused, enabling creative and unique problems - such as working backward from a randomly generated result to determine an original value.
   

   You calculated R = 0.0811 L-atm/mole-K using your lab values. What initial mass of NaHCO₃ would yield R = 0.08205 L-atm/mole-K, assuming all other variables remain the same and the water vapor pressure is 25.1 torr?

2. random numbers - Chem21Labs can generate random numbers with specified ranges and significant figures for algorithmically similar problems. In the example above, the "new" final value (0.08205) can be fixed for all students or randomly generated (e.g. 0.08205 ± 0.00100). Either approach produces unique answers - though randomization is preferred when students work in pairs.
3. arrays - the Chem21Labs program can hold information in arrays. The "answer array" for the lab equipment below is
   
   "thermometer","beaker","buret","flask" . . . . . "watchglass","Buchner funnel"
   This post-lab question asks students to identify 9 of 18 images. Random numbers determine which items to answer (e.g. Q1 or Q2; Q3 or Q4 . . . . Q 17 or Q18). If the first random number is 2, the student answers Q2 and the correct response is the second item in the array, beaker.
   
   

There are many ways to implement this approach - just describe what you need, and we'll make it happen.

We welcome the challenge.