Chemistry 11 Review

Atomic Structure & Periodicity

100

What are the three main subatomic particles, and what are their charges?

Protons (positive), neutrons (neutral), and electrons (negative)

200

An atom has an atomic number 17 and a mass number of 37. How many protons, neutrons, and electrons does a neutral atom of this element have?

17 protons, 20 neutrons, and 17 electrons.

300

Why does atomic radius generally decrease from left to right across a period?

The number of protons increases while electrons are added to the same principal energy level. The increased effective nuclear charge pulls the electrons closer to the nucleus.

400

Which has the larger atomic radius: Na or Mg? Explain your reasoning.

Na. Both are in period 3, but Mg has more protons and therefore greater effective nuclear charge, pulling its electrons closer to the nucleus.

500

An element has the electron configuration 2-8-7.

1. What element is it?
2. What ion would it most likely form, and why?

• The element is chlorine (Cl) because it has 17 electrons.

• It would most likely form a Cl⁻ ion by gaining one electron. This gives it a full outer energy level with 8 valence electrons, making it more stable.

Chemical Bonding

100

What type of bond forms when electrons are transferred from one atom to another?

An ionic bond.

200

What type of bond exists between two non-metal atoms when they share electrons?

A covalent bond.

300

Draw the Lewis structure for CO₂.

O = C = O

Each oxygen has two lone pairs, while carbon has no lone pairs.

400

Why does H₂O have a bent molecular shape rather than a linear shape?

Oxygen has two bonding pairs and two lone pairs of electrons. The electron pairs repel each other, producing a bent molecular geometry.

500

Consider CO₂ and H₂O. Both contain polar covalent bonds, but only one molecule is polar. Identify which molecule is polar and explain why.

H₂O is polar. Its bent shape means the O–H bond dipoles do not cancel. CO₂ has polar C=O bonds, but its linear, symmetrical shape causes the bond dipoles to cancel, making the molecule non-polar.

Chemical Quantities

100

What is Avogadro's number?

6.02 × 10²³ particles per mole.

200

How many moles are present in 36.0 g of H₂O? 

(Molar mass H₂O = 18.0 g/mol)

n=M/m

n=36/18 =2.00 mol

300

How many molecules are present in 0.500 mol of CO₂?

0.500(6.02×10²³) 

=3.01×10²³ molecules

400

Calculate the percentage by mass of oxygen in CaCO₃.

(Ca = 40.1 g/mol, C = 12.0 g/mol, O = 16.0 g/mol)

40.1+12.0+(3)(16.0)=100.1 g/mol 

Mass of oxygen: 48g

%O = (48/100.1) X 100 = 48%

500

A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. Determine its empirical formula.

Assume 100 g:

• C: 40/12=3.33 mol
• H: 6.7/1.0=6.7 mol
• O: 53.3/16.0=3.33 mol

Divide by the smallest:

C:H:O=1:2:1 

Chemical Reactions

100

What type of reaction occurs when two or more substances combine to form one product?

A synthesis reaction.

200

Balance the following equation: H₂+O₂→H₂O

2H₂+O₂→2H₂O

300

Predict the products and balance the reaction: NaCl+AgNO3→? 

NaCl+AgNO₃→AgCl+NaNO₃

400

When 10.0 g of CaCO₃ decomposes according to the equation below, what mass of CO₂ is theoretically produced?

CaCO₃→CaO+CO₂  

(CaCO₃ = 100.1 g/mol; CO₂ = 44.0 g/mol)

10.0÷100.1=0.0999 mol CaCO3

The mole ratio is 1:1:

0.0999 mol CO2 

0.0999(44.0)=4.40 g CO₂

500

A student reacts 5.00 g of H₂ with 32.0 g of O₂:

2H₂+O₂→2H₂O₂

Identify the limiting reactant and determine the theoretical mass of H₂O produced.

Moles H₂:

5.00/2.02=2.48 mol 

Moles O₂:

32.0/32.0=1.00 mol 

The reaction requires 2 mol H₂ for every 1 mol O₂. Therefore, O₂ is the limiting reactant.

1.00 mol O₂ produces 2.00 mol H₂O:

2.00(18.0)=36.0 g H2O 

Solutions & Gases

100

What is the concentration of a solution containing 2.0 mol of solute in 1.0 L of solution?

2.0 mol/L

200

How many moles of NaCl are present in 250 mL of a 0.500 M solution?

n=CV

n=(0.500)(0.250)=0.125 mol

300

What happens to the concentration of a solution when water is added during a dilution?

The concentration decreases because the same amount of solute is distributed throughout a larger volume of solution.

400

A student wants to prepare 500.0 mL of 0.200 M NaCl from a 1.00 M stock solution. What volume of the stock solution is required?

C1V1=C2V2

(1.00)V1=(0.200)(500.0) 

V1=100.0 mL

500

A gas occupies 2.00 L at 25°C. If the temperature increases to 75°C while pressure remains constant, will the volume increase or decrease? Explain using the appropriate gas law.

The volume increases.

Charles's Law states:

V1/T1=V2/T2

Temperatures must be in Kelvin:

25∘C=298K 

75∘C=348K V2=2.00(348/298

V2≈2.34 L 

The gas expands because volume is directly proportional to absolute temperature when pressure is constant.