1. Calcium carbonate and sand mixture with weight of 4 grams is reacted with excees of HCl results in the production of carbon dioxide then find out the percent of calcium carbonate in the original mixture?
2. observe and answer if an unknown compound is noticed to melt at the temperature of 111 degree Celsius with a gas evolution and solidify it, this compound doesn't melt until it reaches at 155 degree Celsius temperature then explain at what time melting of this compound takes place again?