Q: Which of the following numbers is correctly written in scientific notation with the correct number of significant figures?

750 in scientific notation is $$7.50 \times 10^2$

Q: An aqueous solution has $$[\ce{H3O^+}] = 2.5 \times 10$$^{-9}$$\ \text{M} at$$ $$25\ ^\circ\text{C}. $$What is the $$[\ce{OH^-}]$$ concentration?

$$4.0 \times 10$$^{-6}$$\ \text{M}$$

Q: For the reaction $$2\ce{NOBr(g)} \rightleftharpoons 2\ce{NO(g)} + \ce{Br2(g)}$$, $$K_c = 2.00 at$$ $$325\ \text{K}. If$$ $$[\ce{NO}] = 0.110\ \text{M}$$ and $$[\ce{Br2}] = 0.120\ \text{M}$$, what is $$[\ce{NOBr}] at $$equilibrium?

$$1.32 \times 10$$^{-2}$$\ \text{M}$$

Question 1

A reaction at equilibrium is represented as $$\ce{S(s) + H2(g)  H2S(g)}$$ with $$\Delta H = -20\ 	ext{kJ/mol}. $$Which change will shift the equilibrium toward the products?

Accepted Answer

Adding more H2 gas

Question 2

Which of the following numbers is correctly written in scientific notation with the correct number of significant figures?

Accepted Answer

750 in scientific notation is $$7.50 	imes 10^2$

Question 3

Calculate $$2.921 + 14.50 + 5.1$$ and report the answer with the correct number of significant digits.

Accepted Answer

22.5

Question 4

An aqueous solution has $$[\ce{H3O^+}] = 2.5 	imes 10$$^{-9}$$\ 	ext{M} at$$ $$25\ ^\circ	ext{C}. $$What is the $$[\ce{OH^-}]$$ concentration?

Accepted Answer

$$4.0 	imes 10$$^{-6}$$\ 	ext{M}$$

Question 5

A gas mixture at $$298\ 	ext{K}$$ has a total pressure of $$1.20\ 	ext{atm}. $$Argon is $$525\ 	ext{mm Hg}$$, helium is $$202\ 	ext{torr}. $$What is the partial pressure of $$\ce{O2} in mm Hg$$?

Accepted Answer

387 mm Hg

Question 6

For the reaction $$2\ce{NOBr(g)} ightleftharpoons 2\ce{NO(g)} + \ce{Br2(g)}$$, $$K_c = 2.00 at$$ $$325\ 	ext{K}. If$$ $$[\ce{NO}] = 0.110\ 	ext{M}$$ and $$[\ce{Br2}] = 0.120\ 	ext{M}$$, what is $$[\ce{NOBr}] at $$equilibrium?

Accepted Answer

$$1.32 	imes 10$$^{-2}$$\ 	ext{M}$$

Question 7

How many grams of $$\ce{Na2S}$$ are needed to prepare $$225\ 	ext{mL} of$$ $$0.215\ 	ext{M}$$ solution? (Molar mass $$= 78.046\ 	ext{g/mol})$$

Accepted Answer

2.66 g

Question 8

A $$5.00\ 	ext{L}$$ sample of $$\ce{H2O(g)} at$$ $$0.954\ 	ext{atm}$$ and $$648\ 	ext{K}$$ reacts with excess $$\ce{NO2(g)} to $$produce $$\ce{O2(g)}. $$How many grams of $$\ce{O2}$$ are produced? (Molar mass $$= 31.998\ 	ext{g/mol})$$

Accepted Answer

1.66 g

Question 9

Which equilibrium constant represents a reaction that favors the reactants to the greatest extent?

Accepted Answer

$$K_c = 2.5 	imes 10$$^{-8}$$

Question 10

List the acid species in order of increasing acid strength (weakest to strongest): $$\ce{HCO3^-}$$ ($$K_a = 5.6 	imes 10$$^{-11}$$), $$\ce{HCOOH}$$ (K_a = 1.8$$ 	imes $$10^{-4}$$), $$\ce{H2PO4^-}$$ ($$K_a = 6.2 	imes 10$$^{-8}$$).

Accepted Answer

$$\ce{HCO3^-} \u003c \ce{H2PO4^-} \u003c \ce{HCOOH}$$

Question 11

Which intermolecular forces act between a methanol ($$\ce{CH3OH}) $$molecule and a water ($$\ce{H2O}) $$molecule?

Accepted Answer

Dispersion forces, hydrogen bonding, and dipole-dipole forces

Question 12

A $$14.3\ 	ext{g}$$ sample of metal at $$25.0\ ^\circ	ext{C}$$ absorbs $$1.74 	imes 10$$^{-1}$$\ 	ext{kJ} of $$heat to reach $$52.0\ ^\circ	ext{C}. $$What is the specific heat in $$	ext{J/g}^\circ	ext{C}$$?

Accepted Answer

0.451 J/g °C

Question 13

Which one of the following has the least metallic character?

Accepted Answer

Chlorine (Cl)

Question 14

What is the formula of an ionic compound formed from barium and nitrate ions?

Accepted Answer

Ba(NO3)2

Question 15

A nurse prepares an IV of normal saline solution to be delivered at $$1.3\ 	ext{mL/min}. $$How many hours will it take to deliver $$250\ 	ext{mL}$$?

Accepted Answer

3.2 hours

Question 16

During a medical procedure, $$3.68\ 	ext{L} of$$ $$\ce{CO2}$$ gas at $$15.0\ ^\circ	ext{C}$$ and $$1.25\ 	ext{atm} is $$used. What is the final volume at $$37.0\ ^\circ	ext{C}$$ and $$0.785\ 	ext{atm}$$, if the amount of $$\ce{CO2} is $$constant?

Accepted Answer

6.31 L

Question 17

Which combination of aqueous solutions will form a precipitate?

Accepted Answer

Cu(NO3)2(aq) + (NH4)2S(aq)

Question 18

Which of the following electron configurations cannot exist for atoms in their ground state?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^5$$

Solubility and Lewis Structures in General Chemistry

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