UNIT 1

PERIODIC TRENDS

1

Using the periodic table, which element has the larger ionization energy- beryllium or magnesium?

Beryllium 

2

Using the periodic table, which element has the smallest atomic radius- nitrogen, oxygen, or sulfur? 

Oxygen

3

Using the periodic table, which element has the highest electron affinity- germanium or selenium? 

Selenium

4

Why is the first ionization energy for F greater than that of Br in terms of atomic structure and Coulomb's law?

The atomic radius of F is smaller than Br. According to Coulomb's law, the force of attraction is inversely proportional to the distance between charged particles. Since the protons/electrons in F are closer than those in Br, there is a stronger force of attraction and a larger ionization energy. 

5

In terms of atomic structure, why is the atomic radius of gallium smaller than calcium?

Gallium is smaller than calcium because both have four occupied energy shells, but gallium has more protons (31) than calcium (20). Since the valence electron in gallium are more strongly attracted to the nucleus, the atom will be smaller.

MOLES AND MOLAR MASS

1

Using the periodic table, what is the mathematical relationship between moles and mass for carbon, C?

1 mol C = 12.0 g C

2

Using the periodic table, what is the mathematical relationship between moles and mass for NaCl? 

1 mol NaCl = 58.4 g NaCl

3

A chemical reaction consumes 0.85 mol carbon. Using a periodic table, what mass of carbon is consumed in the reaction? 

0.85 mol C x (12 g C / 1 mol C)

= 10.2 g C

4

Using the periodic table, what is the molar mass of Al(NO₃)₃?

26.98 + 42.03 + 144.00

= 213.01 u

5

A sucrose packet contains 4.0 g sucrose, C₁₂H₂₂O₁₁. How many moles of sucrose does the packet contain?

4 g sucrose x (1 mol sucrose / 324.3 g sucrose)

=0.012 mol sucrose

CHEMICAL COMPOSITION OF PURE SUBSTANCES

1

What are the three steps taken to find percent composition?

1. Multiply number of atoms by atomic mass to find mass per element

2. Sum results to find total formula mass

3. Divide mass of each element by total mass and multiply by 100 to find percent of each element.

2

What are the empirical formulas of H₂O₂, Na₂SO₄, and C₂H₄O₂?

H₂O₂ = HO

Na₂SO₄ = Na₂SO₄

C₂H₄O₂ = CH₂O

3

What is the percent composition of sucrose?

42.10% C 

6.49% H

51.40% O

4

What is the empirical formula of a compound that is 28.7% K, 1.5% H, 22.8% P, and 47.0% O?

(1. Convert masses to moles, 2. Divide by lowest number of moles, 3. Use the mole ratio to write the empirical formula)

KH₂PO₄

5

What is the empirical formula of a compound when only the elements C, H, and N are burned completely in O₂ to produce 44.0g CO₂, 45.0g H₂O, and some NO₂?

(Determine the moles of C from CO₂ product, determine moles of H from moles of H₂O product, find the ratio of moles H to moles C)

CH₅N

COMPOSITION OF MIXTURES

1

A 2.4g sample of a mixture of CaCl₂ and NaCl, is found to contain 0.12g Na. What percent of the sample is NaCl?

(Determine moles of Na,  determine moles of NaCl, determine mass of NaCl, calculate percent of NaCl in sample)

13% NaCl

2

A 5.0g sample of a mixture of CaCO₃ and SiO₂ contains 1.5g of Ca. What is the percent CaCO₃ in the mixture?

(1. Determine moles of Ca, 2. Determine moles of CaCO₃, 3. Determine mass of CaCO₃, 4. Calculate percent CaCO₃ in sample)

74.8% CaCO₃ , 75% CaCO₃

3

A 2.70g vitamin C tablet is found to contain 0.0109mol of C₆H₈O₆. What is the mass percent of C₆H₈O₆ in the tablet?

(Calculate mass of C₆H₈O_6, calculate total mass of tablet, multiply by 100)

= 71.1%

4

2.00g sample of Cu and Al are analyzed. Al reacts the copper with HNO₃, as represented by the reaction. It produces 0.010mol Cu(NO₃)₂. What is the percent of Cu by mass in the 2.00g mixture?

Cu_(s)+4HNO_3(aq)->Cu(NO₃)_2(aq)+2NO_2(g)+2H₂O_(l)

(Determine moles of Cu in the Cu(NO₃)₂ product, determine mass of Cu, find percent Cu in the mixture)

=32%

5

A 1.02g magnesium supplement contains 25.0% Mg  by mass. The magnesium is present in the supplement as MgO_(s). How many grams of  are in the magnesium supplement?

(Calculate mass of Mg, calculate moles of MgO, convert moles to g)

=0.423 g MgO

VALENCE ELECTRONS AND IONIC COMPOUNDS

1

1. 1s² 2s² 2p⁴    2. 1s² 2s² 2p⁵

3. [Ne] 3s² 3p¹  4. [Kr] 5s¹

Based on the electron configurations, which of the following two elements are most likely to form an ionic compound with the empirical formula X₂Y?

Element 1 and Element 4

2

Which of the following is the most likely empirical formula of the ionic compound that forms between Ba and Cl?

BaCl₂

3

First- 738, Second- 1451, Third- 7733, Fourth- 10543

^Ionization energy (kj/mol)

Based on the information listed above, which of the following is the most likely empirical formula of the ionic compound that forms between element X and oxygen?

XO

4

The compound CaCl₂ is commonly used as a coagulant in the production of tofu from soy milk.

On the basis of periodic properties, which of the following compounds can most likely also be used in the production of tofu?

-CCl₄, MgCl₂, CaO, CaH₂

MgCl₂

5

Element 1: 1s²2s²2p³ Element 2: [Ne]3s²3p⁴ Element 3: [Kr]5s¹ Element 4: [Xe]6s²

Based on their electron configurations, which of the following two elements are most likely to form an ionic compound with the empirical formula XY?

Element 2 and Element 4