Knowingly or intentionally misrepresenting (or lying about) a material (or important) fact, to induce someone to enter into a transaction is fraud. Fraud can provide a basis to rescind the transaction (i.e. to undo the sale; give the property back, get your money back) or to seek monetary damages or compensation (such as the difference in value between this property at 1.5 acres and it at 0.8 acres). From what you write, there is a reasonable chance you have a case, since claiming an extra 0.7 acres in the advertising and description, if the seller knew or reasonably should have known that was not the case, might well be fraud. If so, you could be entitled to significant compensation. Based on what you write, it would be worthwile to meet with a real estate attorney to discuss this matter in detail and explore your options.