Hemothorax: This term refers to the presence of blood in the pleural cavity, which is the space between the lungs and the chest wall. It is the correct term for "blood in the chest cavity."
Alveolitis: This term refers to inflammation of the alveoli, which are the small air sacs in the lungs where gas exchange occurs. It is not related to blood in the chest cavity.
In summary, the correct term for blood in the chest cavity is hemothorax.