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 trend of electronegativity on the periodic table?

Accepted Answer

Electronegativity increases from left to right across a period and decreases from top to bottom down a group.

Question 10

A neutral atom of magnesium ($$\mathrm{Mg}) $$has an atomic number of 12 and a mass number of 24. How many protons, neutrons, and electrons does it have?

Accepted Answer

12 protons, 12 neutrons, 12 electrons

Question 11

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

Accepted Answer

$$\mathrm{CaCl}_2$$

Question 12

Which of the following molecules is nonpolar?

Accepted Answer

Carbon dioxide ($$\mathrm{CO}_2)$$

Question 13

What is the molar mass of sodium sulfate ($$\mathrm{Na}_2\mathrm{SO}_4$$)?

Accepted Answer

$$142\ \mathrm{g/mol}$$

Question 14

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 15

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 16

Which of the following best describes a cation?

Accepted Answer

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

Question 17

Which of the following is the correct Lewis structure for methane ($$\mathrm{CH}_4$$)?

Accepted Answer

A central carbon atom with four single bonds to four hydrogen atoms, and no lone pairs on carbon.

Question 18

Which of the following best describes the geometry of ammonia ($$\mathrm{NH}_3) $$according to VSEPR theory?

Accepted Answer

Trigonal pyramidal

Question 19

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

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

Question 20

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.

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

Guida di studio - Domande di pratica

Study guide - Flashcard