1 All of the following are clues that a chemical reaction ha

1. All of the following are clues that a chemical reaction has taken place except a) bubbles form b) a change of state occurs for one reactant heat is generated- a solid forms a color change- e) 2. When a precipitation reaction occurs, the ions that do not form the precipitate_ a) are left dissolved in solution b) are cations only care called spectator ions d evaporate e) both a and c

Solution

1:

a) Bubbles formation indicates the chemical reaction occurs because in some chemical reactions gases like H₂ and Cl₂ evolved.

Mg(S) + 2 HCl(aq) -----> MgCl₂(aq) + H₂(g)

b) A change of state does not mean the chemical reaction.

H₂O(l) -------> H₂O(g)

c) In some chemical reaction, heat is generated.

HCl(aq) + NaOH(aq) -----> NaCl(aq) + H₂O(l) + heat

d) In precipitation reaction, solid formation is observed.

Ag⁺ (aq) + Cl^- (aq) ------> AgCl(s)

e) Color change is due to the chemical change of substance.

MnO₄^- (aq)   ------> Mn²⁺ (aq)

(Pink)                     (colorless)

So, a change of state occurs for one reactant is not the clue for chemical reaction.

Answer: (b)