Question

Question 1(Multiple Choice Worth 4 points) (04.02 LC) Which of the following is a synthesis reaction? BaO + CO2 → BaCO3 CH4 + O2 → CO2 + H2O FeCO3 → FeO + CO2 2NH3 → 2N2 + 3H2 Question 2(Multiple Choice Worth 4 points) (04.02 LC) What is true of synthesis and decomposition reactions? Synthesis reactions require more energy than decomposition reactions. Synthesis reactions produce more products than decomposition reactions. Synthesis reactions are the opposite of decomposition reactions. Synthesis reactions have fewer reactants than decomposition reactions. Question 3(Multiple Choice Worth 4 points) (04.02 MC) An unbalanced chemical equation is shown: 2NaN3 → 2Na + N2 Which of the following statements explains why the equation is not balanced? Four molecules of N2 should be produced during the decomposition. Three molecules of N2 should be produced during the decomposition. Four molecules of N2 should be produced during the synthesis reaction. Three molecules of N2 should be produced during the synthesis reaction. Question 4(Multiple Choice Worth 4 points) (04.02 MC) Which chemical equation correctly represents the reaction that takes place when nitrogen gas and hydrogen gas are formed as ammonia decomposes? N(g) + H3(g) → NH3(g) 2N(g) + 3H2(g) → 2NH3(g) 2NH3(g) → N2(g) + 2H3(g) 2NH3(g) → N2(g) + 3H2(g) Question 5 (True/False Worth 2 points) (04.02 LC) A synthesis reaction can be identified because it only has pure elements on the left side of the arrow and compounds on the right side of the arrow. True False Question 6 (True/False Worth 2 points) (04.02 LC) The reaction K(s) + 2H2O(l) → 2KOH(aq) + H2(g) is a decomposition reaction. True False

Answer 1

question-1 The synthesis reaction is: BaO + CO₂ → BaCO₃, as a new compound is synthesized on reaction of BaO and CO₂.

question-2 Synthesis reactions are the opposite of decomposition reactions, as synthesis reaction involves production of few product from more reactants whereas decomposition reaction decomposes reactant to more products.

question-3 Three molecules of N₂ should be produced during the decomposition. The reaction is decomposition reaction.

question-4 The correct reaction is 2NH₃(g) → N₂(g) + 3H₂(g)

question-5 The statement is false because pure element can not undergo decomposition reaction.

question-6 The reaction is false, it is a synthesis reaction as KOH compound is formed on reaction of K and H₂O.

Answer 2

1) Answer is: BaO + CO2 → BaCO3.

Synthesis reaction is a type of reaction in which multiple reactants (in this example barium oxide and carbon dioxide) combine to form a single product (in this example barium carbonate).

New substance, barium carbonate is formed, with different chemical and physical properties than reactants (barium oxide and carbon dioxide).

CH4 + O2 → CO2 + H2O is combustion reaction.

FeCO3 → FeO + CO2 and 2NH3 → 2N2 + 3H2 are decomposition reaction.

2) Answer is: Synthesis reactions are the opposite of decomposition reactions.

Decomposition is reaction where one substance is broken down into two or more simpler substances.

For example, electrolysis of water is the decomposition reaction, because from one molecule (water) two molecules (hydrogen and oxygen) are produced.

Water is separated into two molecules: 2H₂O → 2H₂ + O₂.

Synthesis of water: 2H₂ + O₂ → 2H₂O.

3) Answer is: Three molecules of N2 should be produced during the decomposition.

Balanced chemical reaction: 2NaN₃ → 2Na + 3N₂.

This is decomposition reaction, because from one molecule (sodium nitride) two new substances (sodium and nitrogen) are produced.

According to principle of mass conservation, number of atoms must be equal on both side of chemical reaction.

4) Answer is: 2NH3(g) → N2(g) + 3H2(g).

This is decomposition reaction, because from one pure substance (in this example ammonia) two new pure substances (hydrogen and nitrogen) are produced.  

According to principle of mass conservation, number of atoms must be equal on both side of chemical reaction.  

There are two nitrogen and six hydrogen atoms on both side of balanced chemical reaction.

5) Answer is: False.

The general form of synthesis reaction is:  A + B → AB , where A and B are elements or compounds and AB is a compound.

In synthesis reaction, it can be pure elements or pure chemical compounds on the left side of chemical reaction.

For example, balanced chemical reaction: CaO(s) + H₂O(l) → Ca(OH)₂(aq).

6) Answer is: False.

This is example of single displacement reaction.

Single displacement is reaction where neutral element metal or nonmetal (in this example potassium) become an ion as it replaces another ion (in this example hydrogen) in a compound.

Potassium lose electron and change oxidation number from 0 to +1 (oxidation) and hydrogen gain electron and change oxidation number from +1 to 0 (reduction).