Answer is: buffers. Buffer solution is a solution<span> consisting of a </span>mixture<span> of a </span>weak acid<span> and its </span>conjugate base<span>, or weak base and its conjugate acid. Its pH changes very little when a small amount of </span>strong acid<span> or </span>base<span> is added to it. Buffer solutions keep pH at a nearly constant value. </span>Some buffers are: ethanoic acid and sodium ethanoate, <span>ammonia solution and ammonium chloride.</span>
