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Unit 3 Chemical Reactions

Total questions: 52

Worksheet time: 1hrs 5mins

Name
Class
Date
1.

Which observation would most likely indicate that an endothermic reaction has occurred?

a)

A color change

b)

The production of gas bubbles

c)

An increase in temperature of the surroundings

d)

A decrease in temperature of the surroundings

2.

Which inventory shows the correct names of elements and number of atoms for H2SO4?

a)

Hydrogen = 1 atom; Sulfur = 4 atoms; Oxygen = 4 atoms

b)

Hydrogen = 2 atom; Sulfur = 4 atoms; Oxygen = 4 atoms

c)

Hydrogen = 2 atom; Sulfur = 1 atoms; Oxygen = 4 atoms

d)

Hydrogen = 1 atom; Sulfur = 1 atoms; Oxygen = 4 atoms

3.

Which inventory shows the correct names of elements and number of atoms for NH3?

a)

Nitrogen = 1 atom; Hydrogen = 3 atoms

b)

Nitrogen = 3 atoms; Hydrogen = 3 atoms

c)

Nitrogen = 1 atom; Helium = 3 atoms

d)

Nitrogen = 3 atoms; Helium = 3 atoms

4.

When two clear liquids were combined, a precipitate formed. This most likely means that:

a)

A chemical reaction took place.

b)

The two substances have low boiling points.

c)

One substance dissolved in the other.

d)

The two substances are non-reactive.

5.

Before a chemical reaction, the total mass of two reactants is measured to be 65 grams. After the reaction, what should be the total mass of the products?

a)

0 grams

b)

25 grams

c)

45 grams

d)

65 grams

6.

The idea that matter is neither created nor destroyed in chemical reactions is known as the:

a)

Law of conservation of chemicals.

b)

Law of conservation of energy.

c)

Law of conservation of mass.

d)

Second law of thermodynamics.

7.

During a lab experiment, a scientist numbers three beakers. Next, she pours 150 mL of liquid into each beaker. Each liquid is different. Then, the scientist adds 5 g of white solid baking soda (NaHCO3) to each beaker and stirs. She observes the results. In which of the beakers does the scientist observe clear evidence of a chemical reaction?

a)

Beaker 1 only

b)

Beaker 2 only

c)

Beaker 3 only

d)

Beakers 1, 2, and 3

8.

Which compound has the most atoms?

a)

CO2

b)

C6H12O6

c)

H2O

d)

NaCl

9.

A student sees the following safety symbols associated with a lab assignment. The assignment instructions indicate that a chemical reaction will occur when the student combines two clear non-toxic liquids that are at room temperature. Based on the safety symbols shown above, what evidence of a chemical reaction will the student likely observe?

a)

Release of a toxic gas

b)

Production of a loud sound

c)

Emission of very bright light

d)

Generation of thermal energy

10.

Copper chloride (CuCl2) and aluminum react to produce aluminum chloride (AlCl3) and copper. Which of the following is the correctly balanced chemical equation for this reaction?

a)

CuCl2 + Al → AlCl3 + Cu

b)

3CuCl2 + Al→ AlCl3 + 2Cu

c)

3CuCl2 + 2Al → 2AlCl3 + 3Cu

d)

CuCl2 + 3Al → AlCl3 + 2Cu

11.

Which best describes the difference between physical and chemical changes?

a)

Physical changes only change the size or shape, but chemical changes change the molecular structure and create a new substance.

b)

Chemical changes only change the size or shape, but physical changes change the molecular structure and create a new substance.

c)

Physical changes are always visible changes and chemical changes are never visible.

d)

Chemical changes are always visible changes and physical changes are never visible.

12.

Give the reactants in the following equation:

CH4 + 2O2 → CO2 + H2O

a)

CH4 and CO2

b)

2O2 and CO2

c)

CH4 and 2O2

d)

2O2 and H2O

13.

Give the products in the following equation:

CH4 + 2O2 → CO2 + H2O

a)

CH4 and CO2

b)

2O2 and CO2

c)

2O2 and H2O

d)

CO2 and H2O

14.

Is this equation balanced?

N2 + 3H2 → 2NH3

a)

Yes - it is balanced

b)

No - it is not balanced

15.

Is this equation balanced?

Mg + O2 → MgO

a)

Yes - it is balanced

b)

No - it is not balanced

16.

What are at least 3 the signs a chemical reaction has occurred?

a)

Color change, fizzing, smoke / odor

b)

Bubbles formed, the temperature changed, the only exothermic reaction happened

c)

The temperature changed, only endothermic reaction happened, fizzing.

17.

What is NOT an example of a chemical reaction?

a)

Color change.

b)

Smell / odor.

c)

Freezing.

d)

Change in temperature.

18.

What is the name for the right side of an equation?

(a)  

19.

What is the name for the left side of an equation?

(a)  

20.

Are fireworks an Exothermic or Endothermic reaction? Why?

a)

Exothermic because it's loud, has colors, and gives off smoke.

b)

Endothermic because it takes in heat from its surroundings, and temperature decreases.

21.

How many Carbons are present on the reactant side?

a)

1

b)

2

c)

3

d)

4

22.
A scientist performed four investigations using eight different liquids. In each investigation, the scientist combined two of the liquids and recorded observations. In which investigation is it LEAST likely that the liquids reacted chemically?
a)
1
b)
2
c)
3
d)
4
23.

What is "Conservation of Mass"?

a)

Combination of one or more substances to create one or more different substances

b)

Physical change of state in which identity of the substances remains the same

c)

Law stating that the mass of products equals the mass of reactants

d)

Open system in which some matter escapes

24.

In the chemical equation pictured, if 24 grams of C5H11NH2 is added to O2 to produce a total of 30 grams of product, how many grams of O2 would need to be used?

a)

54 grams

b)

6 grams

c)

15 grams

d)

12 grams

25.

Energy is ______ when bonds break.

a)

gained

b)

lost

c)

released

d)

absorbed

26.

Energy is _____ when new bonds form.

a)

absorbed

b)

released

c)

lost

d)

gained

27.

An _______ reaction is when more thermal energy is released than is absorbed.

a)

endothermic

b)

endergonic

c)

exothermic

d)

exergonic

28.
What is the Law of Conservation of mass?
a)
Mass is created in a chemical reaction
b)
Mass is created in a physical change
c)
New chemicals formed from a chemical reaction have a larger overall mass than the original reactants
d)
Mass is never created or destroyed
29.
In a reaction A + B ----> C,  reactant A has 5g and product  C has 9g. How many grams does reactant B should have? 
a)
4g
b)
5g
c)
9g
d)
14g
30.
If a reaction starts with a total 75g of reactants it should produce 
a)
a total of 40g of products
b)
a total of 75g of products
c)
a total of 180 g of products
d)
None of the above
31.
In the reaction AB-----> A + B reactant AB has 12g and product B has 5g. How many grams should product A have?
a)
17g
b)
2g
c)
7g
d)
None of the above
32.
In the reaction shown by the equation, 252 grams of FeCl2 and 70 grams of Cl2 are consumed.
2FeCl2+ Cl2--> 2FeCl3 
How many grams of FeCl3 are produced? 
a)
161 grams
b)
182 grams
c)
322 grams
d)
392 grams
33.

Sodium and chlorine combine to form sodium chloride, or table salt. Sodium and chlorine are:

a)

Producers

b)

Products

c)

Reactionaries

d)

Reactants

34.

4 grams of hydrogen and 32 grams of oxygen will combine to form:

a)

36 grams of water

b)

28 grams of hydroxide

c)

32 grams of oxygen

d)

36 grams of deuterium

35.

What is the part of the chemical equation in green called?

Fe + S → FeS

a)

products

b)

reactants

c)

yield

d)

input

36.
A chemical equation tells us 
a)
the reactants and the products.
b)
the elements that make up the reactants and the products.
c)
the number of atoms that make up the reactants and the products.
d)
All of the above.
37.
Which is the name of the kind of solid substance formed in this figure?  
a)
aqueous 
b)
precipitate
c)
acid
d)
synthesis 
38.
Describes the number of atoms in a compound of each element. 
a)
coefficient 
b)
superscript 
c)
subscript 
d)
SI unit 
39.
How many atoms of carbon (C) are in C6H12O6?
a)
3
b)
6
c)
12
d)
24
40.
How many Sodium (Na) are in 6NaCl?
a)
1
b)
12
c)
6
41.
How many Hydrogen are in 4H2O?
a)
6
b)
8
c)
2
d)
4
42.
Which of the following reactions is balanced?
a)
2CH4 + O2 -> CO2 + H2O
b)
CH4 + 2O2 -> CO2 + H2O
c)
CH4 + 2O2 -> CO2 + 2H2O
d)
None of the chemical equations are balanced.
43.

Identify the following process: We light a matchstick.

a)

Physical change

b)

Chemical change

44.

Identify the following process: The food and the air react.

a)

Physical change

b)

Chemical change

45.
What is this ?
a)
a chemical reaction
b)
a mathematical equation
c)
a chemical equation
46.

A process in which one or more substances change into others different substances.

a)

a chemical reaction

b)

a mathematical equation

c)

a chemical equation

47.
When a scientist mixed two chemicals, an exothermic reaction takes place. Which of the following would be proof that the reaction was exothermic?
a)
a change of color
b)
a change of state
c)
a temperature decrease
d)
a temperature increase
48.
In any chemical reaction, the mass of the products is always:
a)
slightly less than the mass of the reactants
b)
much less than the mass of the reactants
c)
the same as the mass of the reactants
d)
greater than the mass of the reactants
49.
A student places a piece of a potato into a container of hydrogen peroxide. One observation the student makes is that bubbles form around the potato. The presence of bubbles might indicate the formation of a new substance because bubbles - 
a)
could show that a gas is forming
b)
always rise to the top of a liquid. 
c)
are almost always perfectly spherical.
d)
usually burst after a few minutes.
50.
Which of the following examples shows that a chemical reaction has occurred? 
a)
A rock breaks into smaller pieces when it is struck with a hammer.
b)
Rust forms on a hammer that has been left outside to long. 
c)
A cup of water turns pink when a few drops of red food coloring are added. 
d)
A solid is formed when heat is removed from a sample of water. 
51.
A precipitate is a 
a)
liquid that forms when two solids are reacted
b)
a solid that forms when two liquids are mixed
c)
a gas that forms when vinegar and baking soda react
d)
a change of color in a solution
52.

Which of these is NOT a sign that a chemical change has occurred?

a)

A loss of transparency

b)

An unexpected color change

c)

A temperature change

d)

The formation of a precipitate

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