Chemical Reactions and Balancing Aks

Using the Law of Conservation of Matter, determine the number of grams of iron sulfide (FeS) that will be produced in this reaction.

112g Fe + 64g S → _____ g FeS

• 48 grams

• 112 grams

• 64 grams

• 176 grams

Tags

NGSS.MS-PS1-5

A student is using the above key to model the chemical equation.

How many blue beads will the student need in order to model each side of the equation?

• One for the products and one for the reactants

• Two for the products and two for the reactants

• Two for the products and one for the reactants

• One for the products and two for the reactants

Tags

NGSS.MS-PS1-5

Students want to gather evidence for the claim that the number of atoms before a chemical reaction is equal to the number of atoms after the chemical reaction. They decide to react vinegar and baking soda in a sealed plastic bag. Which of the following would provide the evidence the students need?

• The mass of the plastic bag, baking soda, and vinegar before the reaction was equal to the mass after the reaction.

• Bubbles were produced during the reaction, which meant that a gas was being produced.

• The plastic bag did not change in any way, indicating that it was not involved in the reaction.

• The mass of the baking soda was exactly equal to the mass of the vinegar used to create the chemical reaction.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A teacher performed a demonstration of a chemical reaction by stretching a balloon containing sodium bicarbonate (baking soda) over the top of a flask containing acetic acid (vinegar). When the sodium bicarbonate was added to the acetic acid the balloon began to inflate.

What will the total mass of the flask, the balloon, and products be after the reaction?

• Less than 100 g because some of the solid baking soda disappears

• Less than 100 g because the gas produced by the reaction has less mass than the solids and liquids present before the reaction

• 100 g because all of the atoms of the reactants remain in the closed system

• More than 100 g because the volume of gas inside the balloon has increased

Tags

NGSS.MS-PS1-5

What coefficient should be placed in front of the HCl so that the reaction obeys the Law of Conservation of Mass?

Zn+__HCl → ZnCl₂+H₂

• None

• 1

• 2

• 3

Tags

NGSS.MS-PS1-5

Which of the following is true regarding the atoms involved in a chemical reaction?

• The same number of each type of atom will always be present before and after a chemical reaction takes place.

• Some of the atoms present before the reaction will always be lost during a chemical reaction.

• Some of the atoms will always be changed into a different type of atom by a chemical reaction.

• During a chemical reaction, atoms will always be combined into a much larger molecule.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Students in a science class observed that when a strip of magnesium (Mg) metal was placed in a test tube containing hydrochloric acid (HCl), the magnesium began to bubble as hydrogen gas and magnesium chloride are formed. Which of the following choices show both the correctly balanced equation and identify the type of reaction?

• Mg+2HCl →H₂+MgCl₂ (synthesis)

• 2Mg+HCl →H₂+2MgCl₂ (decomposition)

• Mg+2HCl →H₂+MgCl₂ (single replacement)

• d. Mg+2HCl →2H₂+MgCl₂ (double replacement)

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

When Kay added 30 g of hydrochloric acid (HCl) to 65 g of Zn, bubbles appeared and a white precipitate, zinc chloride (ZnCl2) was produced. She found that the mass of the zinc chloride was 93 g. Since the Law of Conservation of Matter stated that matter cannot be created nor destroyed, she was puzzled about the difference in mass. What is the best explanation for the missing 2 g?

• 2 g of zinc disappeared.

• 2 g of hydrogen gas were produced.

• Kay did not correctly mass the precipitate.

• Kay did not collect all of the precipitate.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which reaction below represents a balanced, decomposition chemical reaction?

• 2MgO → Mg + O₂

• 2KClO₃ → 2KCl + 3O₂

• 2Al + 3Br₂ → 2AlBr₃

• C₅H₁₂ + 8O₂ → 5CO₂ + 6H₂O

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which of the following atomic models of chemical reactions correctly demonstrates the law of conservation of matter?

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Tags

NGSS.MS-PS1-5