Q: Calculate the number of molecules in $$18.0 \text{ g} of $$water ($$H_2O). ($$Molar mass of $$H_2O = 18.0 \text{ g/mol}$$, Avogadro's number $$= 6.02 \times 10$$^{23}$$)

$$6.02 \times 10$$^{23}$$ molecules

Question 1

Which of the following statements best explains why elements form compounds?

Accepted Answer

Elements form compounds to achieve a more stable electron arrangement.

Question 2

What is the maximum number of electrons that can be found in the third energy level ($$n = 3) of an $$atom?

Accepted Answer

$$18$$

Question 3

Which element has the highest electronegativity on the periodic table?

Accepted Answer

Fluorine

Question 4

A sodium atom ($$Na) $$loses one electron to form a sodium ion. What is the charge and electron configuration of the resulting ion?

Accepted Answer

Charge: $$+1$$, Electron configuration: same as neon

Question 5

Which of the following compounds is ionic?

Accepted Answer

NaCl

Question 6

What is the formula for the compound formed between magnesium and hydroxide ions?

Accepted Answer

Mg(OH)$$_2$$

Question 7

How many moles are present in $$12.04 	ext{ g} of $$carbon-12 ($$^{12}C$$)? (Atomic mass of C = $$12.0 	ext{ g/mol})$$

Accepted Answer

$$1.00$$ moles

Question 8

Which of the following molecules is nonpolar?

Accepted Answer

CO$$_2$$

Question 9

What is the molecular shape of methane (CH$$_4) $$according to VSEPR theory?

Accepted Answer

Tetrahedral

Question 10

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally between two atoms.

Question 11

Calculate the number of molecules in $$18.0 	ext{ g} of $$water ($$H_2O). ($$Molar mass of $$H_2O = 18.0 	ext{ g/mol}$$, Avogadro's number $$= 6.02 	imes 10$$^{23}$$)

Accepted Answer

$$6.02 	imes 10$$^{23}$$ molecules

Question 12

Which of the following ions is isoelectronic with neon ($$Ne$$)?

Accepted Answer

Na$$^+$$

Question 13

What is the correct name for the compound $$N_2O_5$$?

Accepted Answer

Dinitrogen pentoxide

Question 14

Which of the following best describes the effect of nonbonded electron pairs on molecular shape?

Accepted Answer

They force bonded pairs closer together, altering bond angles.

Question 15

A compound contains only nonmetals and is named using Greek prefixes. What type of compound is this?

Accepted Answer

Covalent compound

Question 16

What is the formula for calcium phosphate?

Accepted Answer

Ca$$_3(PO$_4$$)$$_2$$

Question 17

Which of the following bonds is nonpolar?

Accepted Answer

C--H

Question 18

If a molecule has polar bonds but is linear in shape, what is the overall molecular polarity?

Accepted Answer

Nonpolar if the dipoles cancel

Question 19

What is the molar mass of magnesium sulfate ($$MgSO_4$$)? (Mg: $$24.3$$, S: $$32.1$$, O: $$16.0)$$

Accepted Answer

$$96.4 	ext{ g/mol}$$

Question 20

Which of the following is the correct Lewis structure for methane ($$CH_4$$)?

Accepted Answer

A central carbon atom with four single bonds to four hydrogen atoms.

Chapter 3: Compounds—How Elements Combine (GOB Chemistry Study Notes)

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