Q: Convert $$2.5 \times 10^3$ grams to scientific notation in kilograms.

$$2.5 \times 10^0$\ \mathrm{kg}$$

Question 1

Which of the following best describes a homogeneous mixture?

Accepted Answer

A mixture in which the composition is uniform throughout, such as salt dissolved in water.

Question 2

A sample of gold has a mass of $$19.3\ \mathrm{g}$$ and a volume of $$1.00\ \mathrm{cm}^3. $$What is the density of gold in $$\mathrm{g/cm}^3$$?

Accepted Answer

$$19.3\ \mathrm{g/cm}^3$$

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 4

A radioactive isotope has a half-life of 3 days. If you start with $$80\ \mathrm{mg}$$, how much remains after 9 days?

Accepted Answer

$$10\ \mathrm{mg}$$

Question 5

Which of the following best describes the difference between a physical change and a chemical change?

Accepted Answer

A physical change does not alter the chemical composition of a substance, while a chemical change results in the formation of new substances.

Question 6

Which of the following elements is a halogen?

Accepted Answer

Chlorine ($$\mathrm{Cl})$$

Question 7

How many significant figures are in the measurement $$0.00450$$?

Accepted Answer

3

Question 8

Convert $$2.5 	imes 10^3$ grams to scientific notation in kilograms.

Accepted Answer

$$2.5 	imes 10^0$\ \mathrm{kg}$$

Question 9

Which of the following best describes the octet rule?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve eight electrons in their valence shell, similar to noble gases.

Question 10

Which of the following is the correct formula for the ionic compound formed between magnesium and chlorine?

Accepted Answer

$$\mathrm{MgCl}_2$$

Question 11

A molecule of carbon dioxide ($$\mathrm{CO}_2) is $$best described as:

Accepted Answer

A nonpolar molecule with polar bonds.

Question 12

Which of the following statements about the periodic table is correct?

Accepted Answer

Elements in the same group have similar chemical properties.

Question 13

How many protons, neutrons, and electrons are in the isotope $$^{14}\mathrm{C}$$?

Accepted Answer

6 protons, 8 neutrons, 6 electrons

Question 14

Which of the following best describes a cation?

Accepted Answer

An ion with a positive charge formed by losing one or more electrons.

Question 15

What is the molar mass of water ($$\mathrm{H}_2\mathrm{O}$$)?

Accepted Answer

$$18.0\ \mathrm{g/mol}$$

Question 16

Which of the following best describes the difference between accuracy and precision?

Accepted Answer

Accuracy refers to how close a measurement is to the true value, while precision refers to how close repeated measurements are to each other.

Question 17

A sample of a radioactive isotope has an activity of $$800\ \mathrm{Bq}. $$After 2 half-lives, what is the remaining activity?

Accepted Answer

$$200\ \mathrm{Bq}$$

Question 18

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally between two atoms due to a difference in electronegativity.

Question 19

How many electrons can the second energy level (n=2) hold?

Accepted Answer

8

Question 20

A patient receives a dose of $$0.25\ \mathrm{Ci} of a $$radioactive tracer. How many becquerels ($$\mathrm{Bq}) is $$this? ($$1\ \mathrm{Ci} = 3.7 	imes 10$$^{10}$$\ \mathrm{Bq})$$

Accepted Answer

$$9.25 	imes 10^9$\ \mathrm{Bq}$$

GOB Chemistry Study Guide: Chapters 1–3 (Matter, Atoms, Compounds)

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