Q: Using the Bohr model, what is the energy of an electron with $$n=6 in a $$hydrogen atom? (Use $$E = -2.178 \times 10$$^{-18}$$\ \text{J} / n^2$)

$$-6.05 \times 10$$^{-20}$$\ \text{J}$$

Question 1

Which of the following is the correct name for the compound Na₂SO₃?

Accepted Answer

Sodium sulfite

Question 2

A magnesium ion, Mg²⁺, has how many protons and electrons?

Accepted Answer

12 protons, 10 electrons

Question 3

A steel sphere has a radius of 1.68 inches. The density of steel is 7.88 g/cm³. 1 inch = 2.54 cm. What is the mass of the sphere in grams? (Use $$V = \frac{4}{3}\pi r^3$)

Accepted Answer

1,040 g

Question 4

What is the molarity of a solution made by dissolving 26.0 g BaCl₂ (molar mass = 208.2 g/mol) in enough water to make 450.0 mL?

Accepted Answer

0.539 M

Question 5

A compound contains only C, H, and O. It is 54.53% C and 9.15% H by mass. Its molecular weight is approximately 88 g/mol. What is its molecular formula?

Accepted Answer

C₄H₈O₂

Question 6

In the reaction $$2A + 3B \rightarrow 3C$$, when 3 moles of A react with excess B, how many moles of C are produced, and what is the limiting reagent?

Accepted Answer

4.5 mol C, A limiting

Question 7

A sample of 70.5 mg of potassium phosphate (K₃PO₄, molar mass = 212.27 g/mol) is added to 15.0 mL of 0.050 M silver nitrate (AgNO₃). The unbalanced equation is: $$\mathrm{K_3PO_4(aq) + $$AgNO_3$$(aq) \rightarrow Ag_3PO_4(s) + $$KNO_3$$(aq)}. $$What is the limiting reactant?

Accepted Answer

AgNO₃

Question 8

If 5.0 g of copper cools from 35°C to 22.6°C and loses 23.6 J of heat, what is the specific heat of copper? (Use $$q = mc\Delta T)$$

Accepted Answer

0.076 J/g°C

Question 9

Which of the following combinations of quantum numbers is allowed?

Accepted Answer

$$n=3,\ l=0,\ m_l=0,\ m_s=-\frac{1}{2}$$

Question 10

Using the Bohr model, what is the energy of an electron with $$n=6 in a $$hydrogen atom? (Use $$E = -2.178 	imes 10$$^{-18}$$\ 	ext{J} / n^2$)

Accepted Answer

$$-6.05 	imes 10$$^{-20}$$\ 	ext{J}$$

Question 11

What is the formal charge on the bromine atom in BrO₃⁻ drawn with three single bonds?

Accepted Answer

-2

Question 12

Which molecule below is polar?

Accepted Answer

PBr₃

Question 13

Which of the following molecules violates the octet rule?

Accepted Answer

SF₆

Question 14

The molecular orbital diagram for N₂ predicts a bond order of:

Accepted Answer

3

Question 15

Which of the following is a strong electrolyte in aqueous solution?

Accepted Answer

KNO₃

Question 16

Determine the oxidation number of sulfur in $$\mathrm{Na_2SO_3}.$$

Accepted Answer

+4

Question 17

A sample of gas occupies 12.5 L at 2.15 atm and 315 K. How many moles of gas are present? (Use $$PV = nRT$$, $$R = 0.0821\ 	ext{L·atm·mol}^{-1}	ext{K}^{-1})$$

Accepted Answer

1.25 mol

Question 18

Which conditions cause a real gas to deviate most from ideal behavior?

Accepted Answer

Low temperature, high pressure

Question 19

Which pair of elements would most likely form an ionic compound?

Accepted Answer

O and Zn

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