Q: Which of the following is the correct formula for calculating the percent composition by mass of an element in a compound?

$$\dfrac{\text{mass of element in 1 mol of compound}}{\text{molar mass of compound}} \times 100\%$$

Question 1

Which of the following ions is always soluble in water, regardless of the anion it is paired with?

Accepted Answer

$$	ext{NO}_3^-$$

Question 2

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula of this compound?

Accepted Answer

$$	ext{CH}_2	ext{O}$$

Question 3

Which of the following molecules has a trigonal planar electron geometry and a bent molecular shape?

Accepted Answer

$$	ext{SO}_2$$

Question 4

A sample of gas occupies 2.50 L at 1.00 atm and 300 K. What will be its volume at 2.00 atm and 300 K?

Accepted Answer

$$1.25\ 	ext{L}$$

Question 5

Which of the following statements about the electromagnetic spectrum is correct?

Accepted Answer

Infrared light has a lower frequency than visible light.

Question 6

Which of the following compounds is insoluble in water?

Accepted Answer

$$	ext{BaSO}_4$$

Question 7

What is the oxidation state of sulfur in $$	ext{SO}_4$$^{2-}$$?

Accepted Answer

+6

Question 8

Which of the following best describes the molecular geometry of $$	ext{PCl}_5$$?

Accepted Answer

Trigonal bipyramidal

Question 9

A solution is prepared by dissolving 5.85 g of NaCl in enough water to make 500.0 mL of solution. What is the molarity of the solution? ($$	ext{NaCl}$$ molar mass = 58.5 g/mol)

Accepted Answer

$$0.20\ 	ext{M}$$

Question 10

Which of the following ions forms a precipitate when mixed with a solution containing $$	ext{AgNO}_3$$?

Accepted Answer

$$	ext{Cl}^-$$

Question 11

Which of the following is the correct formula for calculating the density of a substance?

Accepted Answer

$$d = \dfrac{m}{V}$$

Question 12

Which of the following elements is a halogen?

Accepted Answer

Chlorine

Question 13

What is the wavelength (in nm) of light with a frequency of $$6.00 	imes 10$$^{14}$$\ 	ext{Hz}$$? (Speed of light $$c = 3.00 	imes 10^8$\ 	ext{m/s})$$

Accepted Answer

$$500\ 	ext{nm}$$

Question 14

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

Accepted Answer

Elements in the same group have similar chemical properties.

Question 15

Which of the following is the correct formula for calculating the percent composition by mass of an element in a compound?

Accepted Answer

$$\dfrac{	ext{mass of element in 1 mol of compound}}{	ext{molar mass of compound}} 	imes 100\%$$

Question 16

A 10.0 g sample of $$	ext{CaCO}_3 is $$heated and decomposes according to the equation: $$	ext{CaCO}_3 (s) ightarrow 	ext{CaO} (s) + 	ext{CO}_2 (g). $$What is the theoretical yield of $$	ext{CO}_2 (in $$grams)? (Molar masses: $$	ext{CaCO}_3 = 100.0 g/$$mol, $$	ext{CO}_2 = 44.0 g/$$mol)

Accepted Answer

$$4.40\ 	ext{g}$$

Question 17

Which of the following molecules is nonpolar?

Accepted Answer

$$	ext{CO}_2$$

Question 18

Which of the following ions is most likely to form a precipitate with $$	ext{SO}_4$$^{2-}$$ in aqueous solution?

Accepted Answer

$$	ext{Ba}^{2+}$$

Question 19

Which of the following is the correct formula for the relationship between energy, frequency, and Planck's constant?

Accepted Answer

$$E = h 
u$$

Question 20

Which of the following best describes the electron geometry and molecular shape of $$	ext{CH}_4$$?

Accepted Answer

Tetrahedral, tetrahedral

Essential Tables, Formulas, and Concepts for Introductory Chemistry

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