Physical Science - Chemical Reactions Unit 4 Test - Answers
1-Which of the following equations shows a chemical change?
Answer-C3H8 + 5O2 → 3CO2 + 4H2O
2-How many atoms of carbon (C) are present in the reactants of the following chemical equation?C7H16 + O2 → CO2 + H2O
Answer-7 atoms
3-Use the equation to answer the question. CH4 + 2O2 → CO2 + 2H2O
If you change the 2 in front of to a 3, what will be the change in the results on the right side of the equation?
Answer-There is an extra O2 molecule left over
4-According to the Law of Conservation of Matter, what happens to atoms during a chemical reaction?
Answer-The atoms are rearranged to form new substances.
5-According to the Law of Conservation of Mass, if 88 g of carbon dioxide (CO2) is produced in a reaction between oxygen (O) and 24 g of carbon (C), what is the mass of dioxygen (O2) in the reactants?
Answer-64 g
6-Which statement comparing ionic and covalent bonds is correct?
Answer-Covalent bonds tend to be less polar than ionic bonds.
7-Acid-base reactions can also be classified as which type of reaction?
Answer-double replacement
8-Which statement correctly compares synthesis and decomposition reactions?
Answer-Synthesis and decomposition reactions are opposites of each other. Synthesis reactions are in the form A + B → AB, while decomposition reactions are in the form AB → A + B.
9-Aluminum oxide, Al2O3, decomposes into aluminum, Al, and oxygen gas, O2. Which ratio of aluminum to oxygen gas is in the products of the reaction?
Answer-4:3
10-The left side of a chemical reaction is shown.
Cu + AgNO3 →
Which type of reaction will the reactants undergo?
Answer-single displacement
11-Which phrase describes an oxidizing agent?
Answer-a substance that gains an electron in a reaction
12-Which event is an example of an exothermic reaction?
Answer-combustion
13-Use the reaction to complete the sentence.
2CO + O2 → 2CO2
Carbon monoxide and oxygen combine to produce carbon dioxide. The total bond energy of the products is 1,472 kJ. The bond energy of each carbon-oxygen double bond in carbon dioxide is _____.
Answer-736 kJ
14-Use the table to answer the question.
Which statement about the change in bond energy of this reaction is correct?
Answer-The reaction is exothermic because the total bond energy of the reactants is less than the total bond energy of the products.
For the last written questions good luck! Sorry.
These answers are for a test taken in 2022
