[[alternative]]A INVESTGESTION ON THE 12th GRADE S’ MISCONCEPTIONS OF ACID-BASE-SALT.

[[abstract]]Investigated were the misconceptions of acid-base-salt of the 12th grades’ students. Three hundreds and thirty-five students who had studied acid-base-salt participated in the study. Twenty-four multiple-choose test was developed by the researcher. The test was validated by three high school teachers , the reliability (α) of the test is 0.75. Data was analyzed through descriptive statistics and Pearson product-moment correlations . Major findings are : 1)students judged the pH value of weak acid solutions by using Ka value directly; 2)students didn’t understand the relationship about Ka and strength of acid; 3)when two weak acids were mixed together students counted the concentration of hydrogen ion of the solution without the concept of competition in the reaction；4)students were confused with the solution of Na2CO3 about how they hydrolysis with water, and how come they will be acidic or basic. The study recommended more emphasis on teaching the calculation of Ka , concept of competition and buffer solutions . Further studies related to hydrolylsis of Na2CO3 and the reasons why students thought using same titer in different solutions result in the same pH while neutralization are suggested.