Q: Can I use a 85w magsafe of a macbook pro to charge a macbook black?

See the quote below from Find the right power adapter and cord for your Mac notebook - Apple Support

I'm not sure if they both use the same connector but there is more information in the above link.

Power adapters for Apple notebooks are available in 45W, 60W, and 85W varieties. You should use the appropriate wattage power adapter for your Apple notebook. You can use a higher wattage adapter without issue, but doing this won't make your computer charge faster or operate any differently. Lower wattage adapters will not provide enough power.

Yes you can use it if it will fit. It won't damage the computer due to the wattage but I'm not sure if the connector will fit.

A few resellers of Apple products offer the MagSafe port adapter so newer charger will fit

some of the older magnetic ports. I've seen them online, when not looking to buy one.

Another source for replacement original equipment MagSafe power supplies for older

MacBook models to check into, may be OWC macsales.com. Check to be sure of a

best match, or talk to someone at such companies before purchase. Helps to be able

to correctly identify the computer so that a knowledgeable reseller can match one up.

Good luck & happy computing!