1. Unit 4 Review
Callie Buffington

2. New substances formed during a chemical reaction are indicated as -
A. On the right side of the equation and are called products.
B. On the left side of the equation and are called products
C. On the right side of the equation and are called reactants.
D. On the left side of the equation and are called reactants.

3. What is a coefficient?
A. the number placed in front of a chemical formula in a chemical equation; represents the number of molecules of that substance.
B. 2 H2S + 4 CO2  CH3 + ………….The first big 2
C. the number written to the right and slightly below an element in a chemical formula; represents the number of atoms of an element present in a chemical formula.
D. Both A and B

4. The arrow is normally called a _________ sign.
A. Precipitate
B. Coefficient
C. Subscript
D. Yields

5. Which of the following is a TRUE statement?
A. In a chemical equation, the reactants and products can have different numbers of atoms for each element.
B. In a chemical equation, the coefficients tell you the number of molecules of each reactant used and the number of molecules of each product made.
C. In a chemical equation, you can end up with a different number of atoms of an element on the reactant side for the same element on the product side.
D. In a chemical equation, an element or compound must be ac companied by a phase change.

6. All chemical equations must be balanced
All chemical equations must be balanced. This means that the same number of atoms of each of the elements must be found in both the reactants and the products of the reaction. Which scientific law does this illustrate?
A. Law of Superposition
B. Law of Reflection
C. Law of Conservation of Mass
D. Law of Conservation of Energy

7. A student makes two clear solutions
A student makes two clear solutions. Which of the following is evidence that a chemical reaction is happening?
A. color change, odor change
B. color change, odor change, temperature change, precipitate
C. odor change, temperature change
D. odor change, temperature change, precipitate

8. The following diagram is a model of a molecule of carbon dioxide
The following diagram is a model of a molecule of carbon dioxide. What is the formula for carbon dioxide?
C3H2
CO3
COH3
CO2

9. The following diagram is a model of Hydrogen Sulfide
The following diagram is a model of Hydrogen Sulfide. What is the formula for Hydrogen Sulfide?
A. H2S
B. HS4
C. H4S4
D. H2S2

10. Which of the following shows rust (Fe2O3) forming when oxygen (O2) reacts with iron (Fe)?
A. 2Fe2O3 + 4Fe  3O2
B. 3O2 + 4Fe  2Fe2O3
C. 4Fe  3O2 + 2Fe2O3
D. 2Fe2O3  3O2 + 4Fe

11. Which of the following is a limitation of the model?
Hydrogen
Oxygen
A. The model does not show what the products of the reaction are.
B. The model does not show why the atoms are bonding.
C. The model does not show what the reactants of the reaction are.
D. The model does not show the number of atoms involved in the reaction.

12. What does the thermometer read?
A. 30 degrees Fahrenheit
B. 30 degrees Celsius
C. 34 degrees Celsius
D. 34 degrees Kelvin

13. What does the thermometer read?
A. -11 degrees Celsius
B. -9 degrees Celsius
C. 10 degrees Celsius
D. 9 degrees Celsius

14. If a science question had the word “initial” in it, what does that mean?
A. The letters that begin with someone’s first, middle, and last name.
B. A signature
C. the first reading or measurement
D. the last reading or measurement

15. Be prepared to balance (4) chemical equations on your test…
Be prepared to balance (4) chemical equations on your test…..I can tutor at 7:30 in the mornings….. GOOD LUCK!!!!!!!