The short answer is no, but you're probably asking the wrong question.
There are sanity checks you can make on data that represents an RSA public key, but they don't validate that the public key “actually encrypts”. They validate that the data represents a mathematical object for which the RSA calculations will work (e.g. won't cause a division by zero or an infinite loop).
if i use it to encrypt say a form submission, the form data will actually be encrypted.
If you mean that the form content should be encrypted in transit and that the server should be able to see the plaintext, this doesn't involve RSA at all. Check whether the HTTPS protocol is used for the form submission. The page that displays the form should be HTTPS as well, as well as any other page where you access the site while logged in with the same account. With HTTPS, the contents are encrypted and protected against a man-in-the-middle.
If you mean that the server shouldn't be able to decrypt what you send, why are you sending that data in the first place? But ok, let's assume that you want to send encrypted data to a server, and that the server shouldn't be able to decrypt it.
If you've used RSA correctly, then the only entity that can decrypt the data is whoever has the private key. It's impossible to tell, by looking only at the public key, who has access to the private key.
If you have the private key and you generated the public key from the private key, you don't need to do any validation on the public key. You know it's valid because you obtained it by a correct procedure.
If you don't have the private key and someone gave you the public key, you have to trust them to keep the corresponding private key safe. You can't tell by looking at the public key.
So no, there's no check on the public key that will tell whether your data is securely encrypted. You need to review your whole system architecture.