107) What is the law of conservation of mass?

A) Energy can be created in a reaction
B) The number of reactants must always equal the number of products
C) Mass and energy are interchangeable during reactions
D) Mass can neither be created nor destroyed in a chemical reaction

109) What is the significance of writing physical states in a chemical equation?

A) To provide information about the physical form of substances
B) To show the mass of reactants and products
C) To balance the equation more accurately
D) To indicate the catalyst used in the reaction

110) What is the product formed when slaked lime reacts with carbon dioxide during whitewashing?

A) Calcium hydroxide
B) Calcium carbonate
C) Calcium oxide
D) Calcium chloride

111) Why does the iron nail become brownish when dipped in copper sulfate solution?

A) Copper gets deposited on the nail
B) Iron reacts with oxygen
C) The nail rusts
D) The nail undergoes thermal decomposition