Which of the following chemical reactions would be predicted to occur based on the activity series? A. Ca + BaBr2 → Ba + CaBr2 B. Mn + NiBr2 → Ni + MnBr2 C. Au + PtBr2 → Pt + AuBr2 D. Zn + MgBr2 → Mg + ZnBr2

Based on the activity series, B. Mn + NiBr2 → Ni + MnBr2 would be predicted to occur.

The activity series is a list of elements ordered by their ability to displace hydrogen from acid solutions, and more broadly, by their ability to displace other elements in compounds during a chemical reaction. In an activity series, highly reactive metals are placed at the top, while less reactive metals are placed at the bottom. Elements can typically replace elements that are below them on the activity series in chemical reactions but not the ones above them.

Therefore: - Calcium (Ca) is higher on the activity series than Barium (Ba), but since Ba is already in the compound BaBr2, no displacement will occur, and reaction A is incorrect. - Manganese (Mn) is higher on the activity series than Nickel (Ni), so Mn can replace Ni in the compound NiBr2, making reaction B correct. - Gold (Au) and Platinum (Pt) are both low on the activity series, but because Au is below Pt, it cannot replace Pt in PtBr2, so reaction C is incorrect. - Zinc (Zn) is higher than Magnesium (Mg) on the activity series, but the difference is not sufficient for Zn to replace Mg in MgBr2 easily, and therefore reaction D might not proceed or would proceed very slowly under standard conditions.

Since only reaction B involves a metal that is higher on the activity series displacing another metal that is lower, it is the one predicted to occur.