Q: How many hydrogen atoms are in a 1.0 g sample of acetic acid, CH$$_3$$COOH? The molar mass of acetic acid is 60.05 g/mol.

$$4.0 \times 10$$^{22}$$ atoms H

Question 1

A 16.01 g sample of N$$_2$$ reacts with 3.00 g of H$$_2 to $$form ammonia (NH$$_3). $$What mass of ammonia is formed?

Accepted Answer

17.18 g

Question 2

Determine the limiting reactant (LR) and the mass (in g) of nitrogen that can be formed from 50.0 g NO$$_2$$ and 45.0 g N$$_2H$_4. $$Some possibly useful molar masses are as follows: NO$$_2 = 46.02 g/$$mol, N$$_2H$_4 = 32.05 g/$$mol, N$$_2 = 28.02 g/$$mol. NO$$_2H$_4 + 2 NO$_2H$_4$$ → 3 N$$_2(g) + 4 H$_2O(l)$$

Accepted Answer

LR = NO$$_2$$, 28.2 g N$$_2$$ formed

Question 3

What is the energy of a photon with a wavelength of 245 nm?

Accepted Answer

$$8.11 	imes 10$$^{-19}$$ J

Question 4

Which electronic transition in a hydrogen atom is associated with the largest emission of energy?

Accepted Answer

$$n = 2 \rightarrow n = 1$$

Question 5

How many hydrogen atoms are in a 1.0 g sample of acetic acid, CH$$_3$$COOH? The molar mass of acetic acid is 60.05 g/mol.

Accepted Answer

$$4.0 	imes 10$$^{22}$$ atoms H

Question 6

What is the empirical formula of a compound that contains 72.0% carbon, 12.0% hydrogen and 16.0% oxygen by mass?

Accepted Answer

C$$_6H$_{12}O$$

Question 7

Which molecule contains carbon with a negative formal charge?

Accepted Answer

CO

Question 8

Which set of quantum numbers is correct and consistent with $$n = 4$$?

Accepted Answer

$$n = 4, \ l = 2, \ m_l = -2, \ m_s = +1/2$$

Question 9

What is the correct order of size (from smallest to largest) of K, K$$^+$$, Ca and Ca$$^{2+}$$?

Accepted Answer

Ca$$^{2+}$$ \u003c K$$^+$$ \u003c Ca \u003c K

Question 10

Which species has this ground-state electron arrangement? $$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^6$$ $$3d^{10}$$

Accepted Answer

Zn$$^{2+}$$

Question 11

What is the balanced net ionic equation for the combination of HCl and KOH in water?

Accepted Answer

H$$^+(aq) + OH$^-(aq$$) → H$$_2O(l)$$

Question 12

Which element is oxidized and what is the oxidizing agent in the reaction below? Fe$$_2O$_3(s) + 3CO(g$$) → 2Fe(s) + 3CO$$_2(g)$$

Accepted Answer

Carbon is oxidized, and the oxidizing agent is Fe$$_2O$_3$$

Question 13

What is the standard molar enthalpy of formation for aluminum oxide (Al$$_2O$_3) $$based on the thermochemical equations provided? 4Fe(s) + 3O$$_2(g$$) → 2Fe$$_2O$_3(s$$) $$\Delta H_f = -1648.4 kJ/$$mol; 2Al(s) + Fe$$_2O$_3(s$$) → 2Fe(s) + Al$$_2O$_3(s$$) $$\Delta H_f = -851.5 kJ/$$mol

Accepted Answer

-1675.7 kJ/mol

Question 14

Which molecule has the smallest bond angle?

Accepted Answer

H$$_2S$$

Question 15

Which pair represents a set of isotopes?

Accepted Answer

$$^{74}Se $$and $$^{76}Se$$

Question 16

What is NOT named correctly?

Accepted Answer

MnO$$_2$$, manganese(II) oxide

Question 17

How many grams of CaCl$$_2 ($$molar mass = 111.0 g/mol) are needed to prepare 4.44 L of 0.500 M CaCl$$_2$$ solution?

Accepted Answer

248 g

Question 18

What is the atomic number of an ion with a -2 charge when it has 18 electrons?

Accepted Answer

20

Question 19

What is the total volume of gases produced when 1.5 L of nitrogen trichloride (NCl$$_3) $$decomposes into chlorine and nitrogen at constant pressure and temperature? 2NCl$$_3(g$$) → N$$_2(g) + 3Cl$_2(g)$$

Accepted Answer

4.5 L

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