The Book of Mormon teaches that hell is forever. However, the late Mormon Apostle, Bruce R. McConkie, states in his book, Mormon Doctrine, that this is not so. So, without further ado, let's see how the Book of Mormon contradicts the Mormon's own teachings with regard to hell.
"And that great pit, which hath been digged for them by that great abominable church, which was founded by the devil and his children, that he might lead away the souls of men down to hell—yea, that great pit which hath been digged for the destruction of men shall be filled by those who digged it, unto their utter destruction, saith the Lamb of God; not the destruction of the soul, save it be the casting of it into that hell which hath no end." 1 Nephi 14:3 (Italics—see Matt. 25:41.)
"And there is a place prepared, yea, even that awful hell of which I have spoken, and the devil is the preparator of it; wherefore the final state of the souls of men is to dwell in the kingdom of God, or to be cast out because of that justice of which I have spoken." 1 Nephi 15:35
"For the kingdom of the devil must shake, and they which belong to it must needs be stirred up unto repentance, or the devil will grasp them with his everlasting chains, and they be stirred up to anger, and perish." 2 Nephi 28:19
"And behold, others he flattereth away, and telleth them there is no hell; and he saith unto them: I am no devil, for there is none—and thus he whispereth in their ears, until he grasps them with his awful chains, from whence there is no deliverance. Yea, they are grasped with death, and hell; and death, and hell, and the devil, and all that have been seized therewith must stand before the throne of God, and be judged according to their works, from whence they must go into the place prepared for them, even a lake of fire and brimstone, which is endless torment." 2 Nephi 28:22-23
"And he spake plainly unto them, that he had been deceived by the power of the devil. And he spake of hell, and of eternity, and of eternal punishment." Jacob 7:18
"Oh then, why did he not consign us to an awful destruction, yea, why did he not let the sword of his justice fall upon us, and doom us to eternal despair? Oh, my soul, almost as it were, fleeth at the thought. Behold, he did not exercise his justice upon us, but in his great mercy hath brought us over that everlasting gulf of death and misery, even to the salvation of our souls." Alma 26:19-20
"Yea, who shall be consigned to a state of endless misery, fulfilling the words which say: They that have done good shall have everlasting life; and they that have done evil shall have everlasting damnation. And thus it is. Amen." Helaman 12:26
"But if it be not built upon my gospel, and is built upon the works of men, or upon the works of the devil, verily I say unto you they have joy in their works for a season, and by and by the end cometh, and they are hewn down and cast into the fire, from whence there is no return.
And he that endureth not unto the end, the same is he that is also hewn down and cast into the fire, from whence they can no more return, because of the justice of the Father." 3 Nephi 27:11, 17
"And thus we see that the Lord did visit them in the fulness of his wrath, and their wickedness and abominations had prepared a way for their everlasting destruction." Ether 14:25