Chemical Formulas and Reactions Unit 1 (2024-2025)

A model of an atom is shown below. An atom of which element is represented by this model?

• Boron (B)

• Carbon (C)

• Neon (Ne)

• Sodium (Na)

Which of the following best describes an electron?

• It has no charge and about the same mass as a proton.

• It has a negative charge and much less mass than a proton.

• It has a positive charge and much more mass than a neutron.

• It has a negative charge and about the same mass as a neutron.

A scientist spilled a few drops of dilute hydrochloric acid (HCl) on a lab table. For safety purposes, the scientist sprinkled some baking soda (NaHCO3) onto the spill. Which observation would provide the best evidence that a chemical reaction occurred?

• The baking soda and hydrochloric acid combined, and bubbles formed.

• The baking soda absorbed the hydrochloric acid.

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

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

Which information could a student determine from only the chemical formula of a protein?

• The color of the protein

• The number of molecules in each sequence that makes up a protein

• The physical arrangement of atoms in the structure of the protein

• The number of atoms of each element in the protein

A teacher asks a student to write the chemical equation for photosynthesis. The student’s response is shown below. The equation is not balanced correctly. Which of these is a balanced equation for photosynthesis?

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Hay is made up of organic compounds. What are the main elements in many organic compounds?

• Helium, carbon, sodium

• Sodium, hydrogen, nitrogen

• Carbon, hydrogen, oxygen

• Radon, oxygen, helium

When trying to identify an unknown element, a scientist determines what other elements the unknown element reacts with chemically. Which property of the unknown element determines the other elements it reacts with?

• The total number of neutrons in the unknown element

• The total number of particles in the nucleus of the unknown element

• The number of protons in the nucleus of the unknown element

• The number of valence electrons in the unknown element

The model of the periodic table below shows the locations of four elements. A student is asked to identify an element that is a pale-yellow brittle solid and does not conduct electricity. At which location in this periodic table would the element most likely be found?

• 1

• 2

• 3

• 4

How many atoms of oxygen are in a molecule of glucose?

The chemical equation shown below represents a reaction that produces fuel for certain cars. Which substance represented in this equation is classified as an element?

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