Chemical Reactions Review:

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Chemical Formulas Indicators Reactions Balanced?

Conserv. Of Mass

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Which information could a student determine from only the chemical

formula of a protein?

Chemical Formulas$100

1. The color of the protein2. The number of molecules in each

sequence that makes up the protein3. The physical arrangement of atoms in the

structure of the protein4. The number of atoms of each element in

the protein

P4 + 3O2 2 P2O3

In the equation above, how many atoms of phosphorus are there in

the product?

Chemical Formulas$200

1. 22. 43. 54. 6

A subscript in a chemical formula tells you _____

Chemical Formulas$300

1. How many total atoms of all kinds are in the compound

2. How many different elements there are in the compound

3. How many atoms of a certain kind are in the compound

4. What the symbol is for a particular element

How many total atoms are there in the compound C8H9NO2

Chemical Formulas$400

1. 42. 53. 194. 20

Which of the following compounds has the greatest

number of elements?

Chemical Formulas$500

1. C2H6

2. CH4

3. NaBr4. HNO2

Your grandmother’s silver necklace turned black over the years. Soap and water will not

clean it, but you can rub off the blackened material on the necklace. What is the

explanation for the blackened material on the necklace?

Indicators$100

1. Soil and oil from the wearer’s neck darkened the necklace

2. A physical change, called rusting, occurred between the silver and air

3. A chemical reaction, called tarnishing, occurred between the silver and air

4. Storing the necklace in a dark jewelry box changed the necklace

Mike did a science experiment for a class project. He placed a white egg into a tall glass vase full of red

wine vinegar. Mike described his observations to the class during the experiment. Which of these

observations most clearly tells Mike that a chemical change occurred?

Indicators $200

1. When the egg was added to the vinegar, the egg’s shell turned light red

2. During the experiment, the egg slowly rose to the surface of the vase

3. The vinegar smelled strong when the top was taken off the bottle

4. Lots of little bubbles appeared on the egg and fizzed to the surface of the vinegar

A student observes some sugar as it is heated and burns. Which observation about the burning sugar provides evidence that a chemical reaction has occurred?

Indicators$300

1. The sugar melts and becomes a liquid2. The temperature of the sugar increases3. The sugar turns black and a gas is produced4. The sugar is white and smells sweet

The pictures below show a blue liquid being added to a clear liquid. Which is the best evidence that a chemical reaction may

have occurred.

Indicators$400

1. The solution turned light blue2. The temperature remained the

same3. A precipitate has formed4. The volume increased

Scientists spilled a solution on a lab table. They sprinkled baking soda on the spill to

clean it up. Which observation would provide the best evidence that a chemical reaction

occurred?

Indicators$500

1. The hydrochloric acid evaporated, leaving only the baking soda

2. Some of the baking soda dissolved in the hydrochloric acid

3. The baking soda and hydrochloric acid combined and bubbles formed

4. The baking soda absorbed the hydrochloric acid

According to this equation, what happened to the carbon and

oxygen?

Reactions$100

1. They combined chemically to form carbon and oxygen

2. They combined chemically to form a new compound

3. They combined physically to form a new mixture4. They combined physically to form a new element

What does the number 3 in 3H2O tell you?

WO3 + 3H2 → W + 3H2O

Reactions$2000

1. The reaction produces 3 water molecules2. The reaction produces 3 atoms of water3. The reaction produces 3 atoms of

hydrogen 4. The reaction produces 6 water molecules

It is important to write chemical formulas properly to show what is happening in a

reaction. Which of the following is true of the equation below?

CaCO3 + 2HCl CaCl2 + H2CO3

Reactions$300

1. The 2 after the CaCl indicates 2 molecules of CaCl

2. The 2 before the HCl indicates 2 molecules of HCl

3. The 3 after the CaCO indicates 3 atoms of CO4. The 3 after the H2CO indicates 3 molecules of

CO

What are the reactants in the formula that produces rust?

4 Fe + 3O2 → 2Fe2O3

Reactions $400

1. Fe2O3

2. Fe3. Fe, O2

4. Fe, 3O2, Fe2O3

Which of the following distinguishes a chemical reaction from a physical

change?

Reactions$500

1. The chemical reaction is reversible2. The properties of the reactants are the

same as the products3. The mass of the reactants is different

from the mass of the products4. A new substance must be created in a

chemical reaction

Which of the following chemical equations is balanced?

Balanced?$100

1. 2HCl + NaOH → H2O + NaCl

2. P4O10 + H2O → 3H3PO4

3. CH4 + 2O2 → 2H2O + CO2

4. Fe2O3 + 2C → 2Fe + CO2

Why isn’t the following chemical equation

balanced?C3H8 + 02 → 3CO2 + 4H2O

Balanced?$200

1. H2O is not on both sides of the equation

2. The number of oxygen atoms is not equal on both sides of the equation

3. The number of hydrogen atoms is not equal on both sides of the equation

4. The number of carbon atoms is not equal on both sides of the equation

A student passes an electric current through melted calcium chloride (CaCl2) producing pure calcium metal (Ca) and chlorine gas (Cl2). What

is the balanced equation for this reaction?

Balanced?$300

1. 2CaCl2 → Ca + 2Cl22. Ca + Cl2 → CaCl2 + Cl

3. Ca + CaCl2 → 2Ca + 2Cl2

4. CaCl2 → Ca + Cl2

All of the following chemical equations are balanced except _____

Balanced?$400

1. C3H8 + 502 → 3CO2 + 4H2O

2. Ca + CaCl2 → 2Ca + 2Cl23. CH4 + 2O2 → 2H2O + CO2

4. Cl2 + 2NaBr → 2NaCl + Br2

Is the equation below balanced?

Balanced?$500

1. Yes, because there are two reactants and two products

2. No, there are too many carbon atoms on the reactant side

3. Yes, because there are three elements on both sides of the equation

4. No, there are not enough carbon atoms on the reactant side

Which of the following is a balanced equation?

Conservation of Mass$100

1. Cl2 + NaBr 2NaCl + Br2

2. Cl2 + 2NaBr 2NaCl + 2Br2

3. Cl2 + 2NaBr 2NaCl + Br2

4. 2Cl2 + NaBr 2NaCl + 2Br2

Which equation shows that the total mass during a chemical reaction stays

the same?

Conservation of Mass$200

1. 12. 23. 34. 4

The table below shows a chemical equation. What is the mass of the water produced?

Conservation of Mass$300

1. 112.5 g2. 50 g3. 200 g4. 250.5 g

What does it mean for a chemical equation to be balanced?

Conservation of Mass$400

1. The reactants and the products are written with the same coefficients

2. The number of reactants is equal to the number of products

3. There are the same number of atoms of each element on both sides of the equation

4. The solid products weigh the same as the reactants

Chemical equations must be balanced. This diagram shows that ___

Conservation of Mass$500

1. The atoms on the reactants side are changed into different atoms on the products side

2. The number of molecules on the reactants side is the same as the number of molecules on the products side

3. The number of atoms in the reactants is equal to the number of atoms in the product

4. The reactants are the same substances as the products

What is the best chemical formula for the substance below?

Pictures$100

1. Fe2 + O4

2. 2FeO3. Fe3O4

4. 3FeO4

The methane molecule below contains _____

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1. One atom2. Two elements3. Two compounds4. Five elements

Which chemical formula matches the molecule below?

Pictures$300

1. CH5N

2. 2CH3N

3. CH5N2

4. CH6N

Is the following equation balanced?

Pictures$400

1. Yes2. No3. Almost

What is the indicator that shows milk has gone through a chemical change

Pictures$500

1. Light produced2. Gas produced3. Precipitate produced4. Temperature change