Plants and Muratic acid. will it harm grass and plants?

Short answer, yes. Any "acid" can be detrimental to grass and plants. Here is how to use it and be safe.

https://www.hunker.com/13427984/the-effects-of-muriatic-acid-on-plants

Water plants and surrounding area very well. Put down as much protection as you can. After using the acid, water again. This will help with minimal damage.

Oooh! don't know for sure, but I recon it might - Put up a barrier.

You will want to cover the plants Muriatic acid is a chemical often used on concrete and masonry. It is extremely caustic topically and it has fumes that can burn the lungs. ... The acid is a component of hydrochloric acid and can be very dangerous to plants, causing injury and even killing them

yes, you should not use any acid around plants.what is your project that you are using muriatic acid?