Modeling Conservation of Mass

1.

Open Ended

5 mins

1 pt

Does this chemical equation follow the Law of Conservation of Mass? Use evidence from the equation to support your response.

H₂ + O₂→ H₂O

Evaluate responses using AI:

OFF

Answer explanation

This equation does NOT follow the Law of Conservation of Mass.

It does not follow the law of conservation of mass because it is not balanced. There are 2 hydrogen atoms on the reactant side and 2 hydrogen atoms on the product side. There are 2 oxygen atoms on the reactant side but only 1 oxygen atom on the product side.

Since there is not the same number of oxygen atoms on both sides, the equation is not balanced. The law of conservation of mass states that mass cannot be created or destroyed. In order to follow this law, the equation needs to have the same number of each element on both sides of the equation.

2.

Multiple Choice

30 sec

1 pt

How many total atoms of chlorine are there in 2NaCl₂?

1

2

3

4

Answer explanation

The coefficient in front Na applies to both Na and Cl. (2 x 2 = 4)

3.

Multiple Choice

1 min

1 pt

Which equation supports this model?

2H₂ + O₂ → 2H₂O

H₂ + O₂ → 2H₂O

2H₂O₂ → 2H₂O

2H₂ + O₂ → H₂O

Answer explanation

Look at the model. There are 2 molecules of H₂ and 1 molecules of O₂ on the reactant side. On the product side, you have 2 molecules of H₂O.

4.

Multiple Choice

5 mins

1 pt

Balance this equation:

Al + O₂→ Al₂O₃

2Al + O₂→ Al₂O₃

4Al + O₂→ 2Al₂O₃

4Al + 3O₂→ 2Al₂O₃

2Al + 2O₂→ 4Al₂O₃

5.

Open Ended

5 mins

1 pt

Balance this equation and then calculate the total atomic mass of the reactants and products.

H₂ + O₂→ H₂O

Evaluate responses using AI:

OFF

Answer explanation

Balanced equation: 2H₂ + O₂→ 2H₂O

Reactants:

H = 4 atoms x 1 = 4

O = 2 atoms x 16 = 32

Total mass: 36 amu

Products:

H = 4 atoms x 1 = 4

O = 2 x 16 = 32

Total mass: 36 amu

6.

Multiple Choice

30 sec

1 pt

Which number represent a coefficient in this equation?

Cl₆ + Na₆→ 3Cl₂Na₂

2

3

6

8

Answer explanation

Coefficient is the number in front of the substance. It tells you how many molecules (or groups) of the substance you have.

7.

Open Ended

5 mins

1 pt

How many atoms of oxygen are on each side of the chemical equation?

4FeS + 7O₂ → 2Fe₂O₃ + 4SO₂

Evaluate responses using AI:

OFF

Answer explanation

Reactant side: 7 x 2 = 14 atoms

Product side: (2 x 3) + (4 x 2) = 14 atoms

8.

Open Ended

3 mins

1 pt

Does this reaction follow the Law of Conservation of Mass? Explain.

Evaluate responses using AI:

OFF

Answer explanation

Yes, this reaction does follow the law of conservation of mass. The mass of the reactants were 300.23g. After the substances were mixed, the mass of the products were 300.23g. The Law of Conservation of Mass states that matter cannot be created or destroyed. Since the mass of the reactants and products are the same, this proves that no matter was created or destroyed during this reaction.

9.

Multiple Choice

1 min

1 pt

Jackie and Josh wanted to do an experiment to demonstrate the Law of Conservation of Mass. To do this, they measured the mass of baking soda and vinegar (reactants) and received a mass of 35g. Then, they mixed the two substances and after the reaction, the mass was measured at 33g. What is the possible explanation as to why the mass was not the same before and after the reaction?

Mass was destroyed in the reaction.

They did not measure correctly.

The students did not include an instrument to capture the gas produced in the reaction.

These two substances do not react so nothing would have happened.

Answer explanation

This reaction needs to be completed in a "closed" system; otherwise, the gas produced will escape, leaving the products to have less mass than the reactants.

10.

Fill in the Blank

30 sec

1 pt

The number written below and to the right of a chemical symbol that shows the number of atoms present in that element is called the _____.

11.

Multiple Choice

30 sec

1 pt

True or False

In a chemical equation, the reactants are on the left and the products are on the right.

True

False

Answer explanation

TRUE! "Reactants react to produce the products"

12.

Open Ended

5 mins

1 pt

Balance this chemical equation:

SnO₂ + H₂ → Sn + H₂O

Evaluate responses using AI:

OFF

Answer explanation

SnO₂ + 2H₂ → Sn + 2H₂O

13.

Multiple Choice

30 sec

1 pt

How many sulfur atoms are on the reactant side of the equation?

Ca₃(PO₄)₂ + 2H₂SO₄ → 2CaSO₄ + Ca(H₂PO₄) ₂

2

3

4

8

14.

Multiple Choice

30 sec

1 pt

How many molecules of HCl are in this equation:

Zn + 2HCl → ZnCl₂ + H₂

1

2

3

4

Answer explanation

2 - Remember, the coefficient in front of HCl tells you the number of molecules.

15.

Multiple Choice

1 min

1 pt

What is the approximate atomic mass of one atom of magnesium?

24

55

95

258

Answer explanation

Magnesium is number 12 on the periodic table and has a mass of approximately 24.31.

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