How to factory reset a MacBook Core 2 Duo

What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

Your Intel Mac doesn't have "Erase All Content and Settings", so start with the section below that.

In addition to the information provided by @D.I. Johnson, I would highly recommend creating a bootable macOS USB installer now while you still can do so just so you have more options available in case you have an issue with Recovery Mode.

Also, if the laptop is using a Hard Drive instead of an SSD, then I would suggest first enabling Filevault and let it complete encrypting the Hard Drive. After Filevault finishes encrypting the Hard Drive, then you can easily follow the instructions in the linked Apple article to perform a simple erase using Disk Utility to destroy access to the data stored on the internal Hard Drive as it will destroy the encryption keys needed to decode the data. Unfortunately Apple's instructions neglect this very important step for older devices.

Edit: Forgot the link to the Apple article for enabling Filevault:

Protect data on your Mac with FileVault - Apple Support

A 2.2ghz Core 2 Duo appears to be a "Mid/Late 2007" model.

Whether you have a Recovery partition available for resetting depends on the macOS version it is running. It must have macOS 10.7 Lion installed to use Recovery.

KingJomo wrote:

How to factory reset apple macbook “core 2 duo 2.2 15” mac OS X

What exact macbook... how far back do you have to go to find a "“core 2 duo 2.2"

The last Apple computers to feature the Intel Core 2 Duo 2.2 GHz processor were discontinued on February 26, 2008

what is the real goal here?

Apple defines obsolete as 7 years or older— you are asking about an ≤ 18 year old computer(?)

A obsolete core 2 duo— I would simply remove the hardrive, you can destroy the drive with a hammer if you have no use for it.