Q: A photon has a wavelength of $$4.00 \times 10$$^{-7}$$\ \mathrm{m}. $$What is its energy? (Use $$h = 6.626 \times 10$$^{-34}$$\ \mathrm{J\cdot s}$$, $$c = 3.00 \times 10^8$\ \mathrm{m/s})$$

$$4.97 \times 10$$^{-19}$$\ \mathrm{J}$$

Question 1

A sample of a compound is found to contain only carbon and hydrogen. When 2.00 g of this compound is completely combusted, it produces 6.60 g of CO$$_2$$ and 2.70 g of H$$_2O. $$What is the mass percent of hydrogen in the original compound? (Atomic masses: C = 12.01, H = 1.008, O = 16.00)

Accepted Answer

13.6%

Question 2

Which of the following statements best describes the Law of Multiple Proportions?

Accepted Answer

When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers.

Question 3

A student measures the mass of a metal cylinder as 13.42 g and its volume as 2.7 mL. What is the density of the cylinder, reported with the correct number of significant figures?

Accepted Answer

$$5.0\ \mathrm{g/cm^3$}$$

Question 4

Which of the following is a chemical change?

Accepted Answer

Rusting of iron

Question 5

A 0.250 M solution of NaCl is prepared by diluting 50.0 mL of a stock solution. What was the concentration of the stock solution if the final volume is 200.0 mL?

Accepted Answer

$$1.00\ \mathrm{M}$$

Question 6

Which of the following compounds is an electrolyte and soluble in water?

Accepted Answer

NaNO$$_3$$

Question 7

What is the net ionic equation for the reaction between aqueous solutions of Na$$_2SO$_4$$ and BaCl$$_2$$?

Accepted Answer

$$\mathrm{Ba$$^{2+}$$(aq) + SO_4$^{2-}(aq) \rightarrow $$BaSO_4$$(s)}$$

Question 8

A sample of gas occupies 4.00 L at 1.00 atm and 300 K. What will be its volume at 2.00 atm and 300 K?

Accepted Answer

$$2.00\ \mathrm{L}$$

Question 9

Which of the following best describes the difference between an atom and a molecule?

Accepted Answer

An atom is a single particle of an element, while a molecule is a group of atoms bonded together.

Question 10

Which of the following sets of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

$$n=2,\ l=2,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 11

A 10.0 g sample of CaCO$$_3 ($$molar mass = 100.1 g/mol) is decomposed by heating. What is the theoretical yield of CO$$_2 (in $$grams) produced? (CaCO$$_3$$ $$\rightarrow$$ CaO + CO$$_2)$$

Accepted Answer

$$4.40\ \mathrm{g}$$

Question 12

Which of the following is the correct electron configuration for a ground-state sulfur atom (Z = 16)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^4$$

Question 13

Which of the following is a molecular compound?

Accepted Answer

CO$$_2$$

Question 14

A 2.00 L container holds 0.100 mol of O$$_2$$ gas at 27$$^\circC. $$What is the pressure in the container? (Use $$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$1.22\ \mathrm{atm}$$

Question 15

Which of the following is the correct balanced equation for the combustion of propane (C$$_3H$_8$$)?

Accepted Answer

$$\mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}$$

Question 16

Which of the following is the correct formula for iron(III) oxide?

Accepted Answer

Fe$$_2O$_3$$

Question 17

Which of the following statements about the first law of thermodynamics is correct?

Accepted Answer

The total energy of the universe is constant; energy can be transferred or transformed, but not created or destroyed.

Question 18

A photon has a wavelength of $$4.00 	imes 10$$^{-7}$$\ \mathrm{m}. $$What is its energy? (Use $$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J\cdot s}$$, $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$4.97 	imes 10$$^{-19}$$\ \mathrm{J}$$

Question 19

Which element is a metalloid?

Accepted Answer

Si

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