|
Correct Answer: ii, iii, and iv.
**correct answer: ii, iii, and iv.**
**explanation:**
the law of conservation of matter states that matter cannot be created or destroyed in an isolated system. during a chemical reaction, this law implies that the total mass of the reactants must equal the total mass of the products. let's analyze each statement in light of this law:
**i. the molecules present after a chemical reaction will be exactly the same as the molecules present before the reaction.**
- this statement is incorrect. if it were true, it would imply that no chemical reaction has occurred. chemical reactions involve the breaking and forming of bonds between atoms, leading to the creation of new molecules from the atoms of the original molecules. thus, the identity and structure of molecules generally change during a reaction.
**ii. the atoms present after a chemical reaction will be exactly the same as the atoms present before the reaction.**
- this statement is true. the law of conservation of matter dictates that all atoms present in the reactants must be present in the products. they may be rearranged and may form different molecules, but the type and number of atoms remain constant throughout the reaction.
**iii. for a chemical reaction that goes to completion, the mass of products will equal the mass of reactants.**
- this statement is true and is a direct restatement of the law of conservation of matter. the mass of the substances involved in a chemical reaction does not change; rather, it is redistributed among the products.
**iv. new molecules that were not present in the reactants can be present in the product of a chemical reaction.**
- this statement is also true. as the atoms are rearranged during a chemical reaction, they can form entirely new molecules that were not present initially in the reactant side. this is the essence of chemical change — forming new substances with properties different from those of the original substances.
in summary, statements ii, iii, and iv accurately reflect the principles of the law of conservation of matter as they apply to chemical reactions, while statement i does not, as it incorrectly suggests that no new molecules are formed in a reaction.
|
ExamEdge's online practice test is that they mimicked the actual exam. I walked into the exam feeling confident I knew the material and walked out knowing my time studying with Exam Edge was well worth the effort."
Back To General Exam Info