Science Assessment ~ Items ~ RG085004

Potassium iodide (KI) and lead nitrate (Pb(NO₃)₂) are two powders that react with each other when mixed together. During the reaction between these two powders, the bonds between the potassium (K) atoms and iodine (I) atoms are broken and bonds between lead (Pb) atoms and iodine (I) atoms form.

2 KI + Pb(NO₃)₂ ---> PbI₂ + 2 K(NO₃)

Which of the following describes the change in energy when the KI bonds break and the change in energy when the PbI₂ bonds form?

Energy is released both when the KI bonds break and when the PbI₂ bonds form.
Energy is required both to break the KI bonds and to form the PbI₂ bonds.
Energy is released when the KI bonds break, and energy is required to form the PbI₂ bonds.
Energy is required to break the KI bonds, and energy is released when the PbI₂ bonds are formed.

Details
Performance
NGSS

Topic: Energy: Forms, Transformation, Transfer, and Conservation
Correct Answer: D
Misconceptions

Distribution of Responses

Chart showing distrubtion of responses for Item EG085004

Scale Score for Item Difficulty (200[Easy]-800[Difficult]): 557

Students Responding Correctly

Group	Correct	Total	Percent
Overall	185	1065	17%
Grades
4–5	N/A	N/A	N/A
6–8	101	644	16%
9–12	84	421	20%
Gender
Male	85	506	17%
Female	97	533	18%
Primary Language
English	155	926	17%
Other	27	112	24%

View data table

Disciplinary Core Ideas: PS1.A A stable molecule has less energy than the same set of atoms separated; one must provide at least this energy in order to take the molecule apart.

Science Assessment

Item RG085004: During the reaction between KI and Pb(NO3)2, energy is required to break the bonds of the reactant molecules, and energy is released when the bonds of the product molecules are formed.