MS PS 1-5 Conservation of Mass

Front

The law of conservation of mass says substances can neither be _______ nor ___________.

Back

Created; destroyed

Answer explanation

The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. Therefore, the correct completion of the statement is 'Created; destroyed', as it reflects this fundamental principle.

Front

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

Back

36 grams of water

Answer explanation

4 grams of hydrogen and 32 grams of oxygen combine in a 2:16 ratio to form water (H2O). The total mass of the products is 36 grams, confirming that the correct answer is 36 grams of water.

Front

In a chemical reaction, 4 grams of sodium must combine with how many grams of chlorine to produce 10 grams of table salt?

Back

6 grams

Answer explanation

To produce 10 grams of table salt, the total mass of sodium and chlorine must equal 10 grams. With 4 grams of sodium, chlorine must be 10 - 4 = 6 grams. Thus, 6 grams of chlorine is needed.

Front

The Law of Conservation of Mass states Matter is NEITHER created nor destroyed.

Back

True

Answer explanation

The Law of Conservation of Mass asserts that matter cannot be created or destroyed in a chemical reaction. Therefore, the statement is True.

Front

How many oxygen atoms are in this chemical formula?

Back

6 oxygen atoms

Answer explanation

The chemical formula contains 3 molecules of a compound, each with 2 oxygen atoms. Therefore, 3 x 2 = 6 oxygen atoms in total, making '6 oxygen atoms' the correct answer.

Front

When a chemical reaction is at equilibrium

Back

There are the same number of atoms on both sides

Answer explanation

A chemical reaction is balanced when both sides have the same number of atoms. This ensures that the law of conservation of mass is upheld, meaning the total mass of reactants equals the total mass of products.

Front

If a reaction starts with a total of 75 grams of reactants, it should produce

Back

a total of 75 grams of products

Answer explanation

According to the law of conservation of mass, the total mass of reactants equals the total mass of products. Therefore, if the reaction starts with 75g of reactants, it will produce a total of 75g of products.

Front

How many nitrogen atoms are in NH₃?

Back

1

Answer explanation

NH3, or ammonia, consists of one nitrogen atom and three hydrogen atoms. Therefore, the correct answer is 1.

Front

Is this balanced?
2HgO → 2Hg + O₂

Back

Yes

Answer explanation

Yes, the equation 2HgO → 2Hg + O2 is balanced. There are 2 mercury (Hg) atoms and 2 oxygen (O) atoms on both sides, satisfying the law of conservation of mass.

Front

Is this equation balanced or unbalanced? CH₄ + 2O₂--> CO₂+ 2H₂O

Back

Balanced

Answer explanation

The equation CH4 + 2O2 --> CO2 + 2H2O is balanced because the number of each type of atom on the reactant side (1 C, 4 H, 4 O) equals the number on the product side (1 C, 4 H, 4 O). Thus, the correct choice is 'balanced'.