Q: Calculate the formula mass of magnesium sulfate, MgSO$$_4 ($$atomic masses: Mg = 24.3, S = 32.1, O = 16.0).

$$24.3 + 32.1 + (4 \times 16.0) = 120.4\ \text{g/mol}$$

Q: How many molecules are present in 18.0 g of water (H$$_2O$$)? (Molar mass of H$$_2O = 18.0 g/$$mol, Avogadro's number = $$6.022 \times 10$$^{23}$$)

$$6.022 \times 10$$^{23}$$ molecules

Q: What is the mass percent of carbon in glucose, C$$_6H$_{12}O$_6$$? (Atomic masses: C = 12.0, H = 1.0, O = 16.0)

$$\frac{6 \times 12.0}{180.0} \times 100\% = 40.0\%$$

Q: A 10.0 g sample of a compound contains 2.0 g of hydrogen. What is the mass percent of hydrogen in the compound?

$$\frac{2.0}{10.0} \times 100\% = 20.0\%$$

Question 1

Which of the following electron configurations represents the ground state of the Fe$$^{2+}$$ ion?

Accepted Answer

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

Question 2

Which of the following species is isoelectronic with Ne?

Accepted Answer

All of the above

Question 3

Which of the following correctly lists the elements in order of increasing atomic radius?

Accepted Answer

F \u003c N \u003c O

Question 4

Which of the following ions has the largest radius?

Accepted Answer

O$$^{2-}$$

Question 5

Which of the following elements is paramagnetic in its ground state?

Accepted Answer

O

Question 6

Which of the following statements about ionization energy is correct?

Accepted Answer

Ionization energy decreases down a group and increases across a period.

Question 7

Which of the following elements has the greatest metallic character?

Accepted Answer

K

Question 8

Which of the following is the correct Lewis dot structure for sulfur (S)?

Accepted Answer

S with 6 dots around the symbol

Question 9

What is the correct formula for the ionic compound formed between calcium and nitrate?

Accepted Answer

Ca(NO$$_3$$)$$_2$$

Question 10

Calculate the formula mass of magnesium sulfate, MgSO$$_4 ($$atomic masses: Mg = 24.3, S = 32.1, O = 16.0).

Accepted Answer

$$24.3 + 32.1 + (4 	imes 16.0) = 120.4\ 	ext{g/mol}$$

Question 11

Which of the following is the empirical formula for a compound with the molecular formula C$$_4H$_{10}$$?

Accepted Answer

C$$_2H$_5$$

Question 12

What is the name of the compound with the formula N$$_2O$_5$$?

Accepted Answer

Dinitrogen pentoxide

Question 13

How many molecules are present in 18.0 g of water (H$$_2O$$)? (Molar mass of H$$_2O = 18.0 g/$$mol, Avogadro's number = $$6.022 	imes 10$$^{23}$$)

Accepted Answer

$$6.022 	imes 10$$^{23}$$ molecules

Question 14

A sample contains 58.5 g of NaCl (molar mass = 58.5 g/mol). How many moles of NaCl are present?

Accepted Answer

$$1.00$$ mol

Question 15

What is the mass percent of carbon in glucose, C$$_6H$_{12}O$_6$$? (Atomic masses: C = 12.0, H = 1.0, O = 16.0)

Accepted Answer

$$\frac{6 	imes 12.0}{180.0} 	imes 100\% = 40.0\%$$

Question 16

If a compound contains 27.3 g of C and 72.7 g of O, what is its empirical formula? (Atomic masses: C = 12.0, O = 16.0)

Accepted Answer

CO$$_2$$

Question 17

A compound has an empirical formula of CH$$_2O $$and a molar mass of 180 g/mol. What is its molecular formula? (Empirical formula mass = 30 g/mol)

Accepted Answer

C$$_6H$_{12}O$_6$$

Question 18

A 10.0 g sample of a compound contains 2.0 g of hydrogen. What is the mass percent of hydrogen in the compound?

Accepted Answer

$$\frac{2.0}{10.0} 	imes 100\% = 20.0\%$$

Question 19

Which of the following best explains why the first ionization energy of Na is lower than that of Mg?

Accepted Answer

Na has a lower nuclear charge and its valence electron is less tightly held.

Question 20

Which of the following pairs of ions are isoelectronic and have the same number of electrons?

Accepted Answer

Na$$^+$$ and Mg$$^{2+}$$

Periodic Properties and Compounds: Study Guide for Chapters 3 & 4

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