Which of the following equations represents an unbalanced neutralization reaction equation? a) hbr + ca(oh)2 → cabr2 + h2o b) so2 + h2o → h2so3 c) nacl + h2o → hcl + naoh d) na + h2o → naoh + h2

When you have to balance an equation it means that you have to balance both parts of equation so that the numbers of each elements will have the same amount. According to this rule, it is quite easy to distinguish unbalanced reaction, and the answer is a) HBr + Ca(OH)2 → CaBr2 + H2O as you can see that amount of oxygen on both sides is not the same.