Chemistry QCE Unit 2

What is the main idea behind VSEPR theory?

Electrons repel each other and arrange themselves as far apart as possible.

In the molecule methane (CH₄), which shape does VSEPR theory predict?

Tetrahedral

Define Electronegativity

How does electronegativity move as a periodic trend

What do London dispersion forces depend on?

Molecular size

What is the polarity of water (H2O)?

Polar

What intermolecular force occurs in H2O?

Hydrogen bonding

What type of force exists in NaCl?

Ionic bond

Which property is affected by intermolecular forces?

Boiling point

What type of molecule is HCl?

Polar

If a substance exhibits only dipole-dipole forces, which state is it most likely to be at room temperature?

Liquids

Which statement best describes the origin of London dispersion forces?

Temporary dipoles created by the random movement of electrons within molecules

According to the description of dipole-dipole forces, which property of polar molecules causes them to align and attract each other?

They possess a permanent dipole moment due to unequal distribution of electrons.

What are the conditions for standard temperature and pressure (STP)?

0 degrees Celsius and 1 atm

At 700 °C and a constant pressure, 36 dm³ of nitrogen gas reacts with hydrogen gas to form ammonia.

a) Write a balanced chemical equation for this process.

1N_2(g)+3H_3(g) → 2NH_3(g)

b) What volume (in dm³) of ammonia gas will be produced if all the nitrogen reacts completely?

36dm³ x 2 = 72

What best explains the difference between acid strength and acid concentration?

Acid strength refers to the degree of dissociation in water, while acid concentration refers to the amount of solute in a given volume.

What best describes an unsaturated solution in terms of solute concentration

It contains less solute than what the solvent can dissolve

A 200 mL sample of a 1.7 M solution of HCl was used in a reaction.

What amount, in mol (n), of HCl is present?

c=n/V

0.34 mol

How much water would need to be added to 150 mL of a 2.0 mol L^-1 solution to achieve a final concentration of 1.5 mol L^-1?

c₁  × V₁=c₂×V₂

0.050 L

What are the customary units of solubility on solubility curves?

Degrees Celsius and grams of solute/100g of water

According to the graph, the solubility of any substance changes as _________ changes.

Temperature

List the substances whose solubility decreases as temperature increases.

NH₃ (ammonia) and Ce2(SO4)₂ (Cerium Sulfate)

Is 45g of NaNO₃ in 100 g of water at 30°C unsaturated, saturated or supersaturated?

Unsaturated