Sadly the CPU chip is soldered on your logic board in this series
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Sadly the CPU chip is soldered on your logic board in this series [https://everymac.com/systems/apple/imac/specs/imac-core-i5-2.3-21-inch-aluminum-mid-2017-specs.html|21.5” iMac Core i5" 2.3 (Mid-2017)]