题目

Hummingbirds have got their name from the distinct “hum” sound made by their rapidly flapping (拍打) wings. The size of the bird decides the number of flaps it can do. The average lifetime of a hummingbird is 3 or 4 years, but some of them have lived beyond 12 years also. They are unique in many ways. Besides the number of rapid flaps they can do per second, they can also fly backwards. Hummingbirds have an amazing sense of assessing the amount of sugar in the nectar (花蜜) they eat. They feed on the nectar of flowers. Hummingbirds do not feed on flowers whose nectar contains less than程明和王刚不小心将纯碱洒到白醋（其有效成分为醋酸，可用HAc表示）里，发现有大量气泡产生，这使他们对醋酸产生了新认识：醋酸像盐酸一样，能与纯碱反应；此外，他们通过查阅相关资料，还检索到以下信息：①醋酸与盐酸都具有较强挥发性；②醋酸是一种有机酸，具有酸的通性，且其钠盐（NaAc）受热不易分解；③盐酸与纯碱的反应分以下两步进行：I．Na2CO3+HCl═NaHCO3+NaCl；Ⅱ．NaHCO3+HCl═NaCl+H2O+CO2↑试根据以上信息回答下列问题：（1）醋酸可以使紫色石蕊试液变    ；（2）根据信息①可知醋酸应置于阴凉处    保存；（3）试写出醋酸与纯碱第一步反应的化学方程式：    ．（4）他们向纯碱溶液中滴加醋酸到不再产生气泡后，将所得溶液蒸发结晶，获得了少量白色固体．王刚认为这就是纯净的NaAc，而程明则认为里面含有HAc．你认为    的观点正确，理由是：    ．