Q: Convert $$0.000456 to $$scientific notation and state the number of significant figures.

$$4.56 \times 10$$^{-4}$$, 3 significant figures

Question 1

Which of the following best describes a chemical property of matter?

Accepted Answer

The ability of iron to rust when exposed to oxygen

Question 2

A sample of a substance has a mass of $$45.0\ \mathrm{g}$$ and a volume of $$15.0\ \mathrm{mL}. $$What is its density, and how many significant figures should your answer have?

Accepted Answer

$$3.00\ \mathrm{g/mL}$$, 3 significant figures

Question 3

Which of the following statements about the scientific method is correct?

Accepted Answer

A hypothesis is a tentative explanation that can be tested by experiments

Question 4

Convert $$0.000456 to $$scientific notation and state the number of significant figures.

Accepted Answer

$$4.56 	imes 10$$^{-4}$$, 3 significant figures

Question 5

Which of the following best describes a heterogeneous mixture?

Accepted Answer

A salad with lettuce, tomatoes, and cucumbers

Question 6

A patient is given a medication with a dosage of $$2.50\ \mathrm{mg}$$ per kilogram of body weight. If the patient weighs $$70.0\ \mathrm{kg}$$, how many milligrams of medication should be administered? (Round to the correct number of significant figures.)

Accepted Answer

$$175\ \mathrm{mg}$$

Question 7

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 8

Which of the following best explains why metals tend to form cations?

Accepted Answer

Metals lose electrons to achieve a stable noble gas electron configuration

Question 9

Which of the following is the correct electron configuration for a neutral atom of sodium ($$\mathrm{Na}$$, atomic number 11)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^1$$

Question 10

Which of the following best describes the difference between an ionic and a covalent bond?

Accepted Answer

An ionic bond involves the transfer of electrons, while a covalent bond involves the sharing of electrons

Question 11

A chemical reaction releases $$150.0\ \mathrm{kJ} of $$energy. Which term best describes this reaction, and what happens to the temperature of the surroundings?

Accepted Answer

Exothermic; the temperature of the surroundings increases

Question 12

Which of the following elements is most likely to form a $$2^+$$ ion?

Accepted Answer

Magnesium ($$\mathrm{Mg})$$

Question 13

Which of the following statements about the Bohr and Quantum-Mechanical models of the atom is correct?

Accepted Answer

The Bohr model describes electrons in fixed orbits, while the Quantum-Mechanical model describes electrons in probability clouds called orbitals

Question 14

A sample of water is heated from $$25.0^\circ\mathrm{C} to$$ $$75.0^\circ\mathrm{C}. If $$the mass of the water is $$100.0\ \mathrm{g}$$ and the specific heat capacity of water is $$4.18\ \mathrm{J/g\cdot ^\circ C}$$, how much energy is absorbed? (Use $$q = m c \Delta T$$ and round to the correct number of significant figures.)

Accepted Answer

$$20,900\ \mathrm{J}$$

Question 15

Which of the following best describes the trend in atomic size across a period from left to right in the periodic table?

Accepted Answer

Atomic size decreases

Question 16

Which of the following molecules is non-polar?

Accepted Answer

Carbon dioxide ($$\mathrm{CO_2$})$$

Question 17

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

Accepted Answer

Elements in the same group have similar chemical properties

Question 18

Which of the following best describes Hund’s rule as it applies to electron configurations?

Accepted Answer

Electrons occupy degenerate orbitals singly before pairing up

Question 19

Which of the following is the correct Lewis structure for a chloride ion ($$\mathrm{Cl^-}$$)?

Accepted Answer

A Cl atom surrounded by 8 dots (valence electrons) and a $$-$$ charge written as a superscript

Question 20

Which of the following best explains why fluorine is the most electronegative element?

Accepted Answer

Fluorine has a high effective nuclear charge and a small atomic radius, so it strongly attracts electrons

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