Question

students are conducting an experiment to identify an unknown solid, and instructed to write their observations. malleable, and soft enough to cut with a knife. reacts explosively with water. displays a yellow flame when exposed to a bunsen burner flame. based on these observations, which is the best prediction for the identity of the unknown? aluminum sodium chromium lead

Explanation:

• Aluminum: It is malleable but does not react explosively with water and does not give a yellow flame in a flame test.
• Sodium: It is a soft, malleable metal (can be cut with a knife). It reacts explosively with water (\(2Na + 2H_2O=2NaOH + H_2\uparrow\), and the reaction is highly exothermic and the hydrogen gas can ignite). In a flame test, sodium gives a bright - yellow flame due to the excitation of electrons in the sodium atoms.
• Chromium: It is a hard metal (not soft enough to be cut with a knife) and does not react explosively with water in the way described.
• Lead: It is a relatively soft metal but does not react explosively with water and does not produce a yellow flame in a flame test.

Answer:

sodium