Rinse Bean Soup Mix and pick out any stones or broken beans. Place beans in a 4 to 5-quart Dutch oven; cover with cool water and soak overnight.
Drain the beans and return to pan. Add 8 cups water, ham hock, garlic, onion, salt and pepper. Cover and bring to a boil. Reduce heat, and simmer 1½ -2 hours or until the beans are tender.
Add chili powder and tomatoes. Simmer 20-30 minutes, stirring occasionally. Remove the ham hock from the soup. Remove the meat from the bone, chop the meat, and return it to the soup. Mash some of the beans to thicken the texture of the soup. Stir in lemon juice. Taste and season with salt and pepper.