HCL is tritrated with NaOH. KHP is then added. A possible source of systematic error in this experiment is failure to dry the KHP. If this occured, would the final wt% NA2CO3 be falsely high, falsely low, or unaffected. Give reasoning. Thanks.

Question

You have left out much of the problem. I can't believe KHP is added after titrating HCl with NaOH. And where does the Na2CO3 come in? I know but you might be able to determine the answer yourself if you organized the facts of the experiment a little better. Please reread and repost with a cleaner post.

It is not certain what you are doing. How is sodium carbonate entering the reaction.

Normally, one uses KHP to determine the molarity of NaOH. If the KHP were wet, too little mass for KHP (some of what you massed was water) would have been recorded, so the molarity of the sodium hydroxide would have been calculated as too low. How this error of low molarity of NaOH affects the rest of the experiment depends on what you did.