UNIT 1 - Stoichiometric Relationships

Question 1

What is an anhydrous salt?

Answer 1

A hydrated salt where the water of crystallization has been driven off by heating.

Question 2

What is the formula for concentration percentage?

Answer 2

Cp=m(s) / m(solution) x100%

where m(solution) = m(solvent)+m(substance)

Question 3

When usually do real gases deviate from ideal gas behavior?

Answer 3

At high pressure and low temperature.

Question 4

What is the formula for converting the temp in Celsius to K?

Answer 4

temp (K) = temp C + 273

Question 5

List the gas laws.

Answer 5

1. Boyle’s law - pressure of a gas is inversely proportional to its volume and their product is constant.
2. Charles’ law - volume of a gas is directly proportional to its absolute temperature and V/T=const
3. Gay-Lussac’s - the pressure of a gas is directly proportional to the absolute temperature and P/T=const

Question 6

What does Avogadro’s law state and why?

Answer 6

That equal volume of all gases, when measured at the same temp and pressure contain an equal number of particles
because the particles of a gas are so widely spread with such negligible forces between them that the chemical nature of it is irrelevant to its volume.

Question 7

What is back titration?

Answer 7

Returning to the end-point after it is passed used when the end-point is hard to identify or the substance is impure.

Question 7

What is a titration?

Answer 7

A volumetric analysis used to determine precisely the reacting volumes of an unknown substance.

A known concentration and volume reacts with the analyte with an indicator present.

Question 7

What constitues a solution?

Answer 7

solute and solvent

Question 8

What does the molecular formula show?

Answer 8

All the atoms present in a molecule.

Question 9

What is the formula for molar concentration?

Answer 9

C = n/V [molxdm-1]

Question 10

What is the empirical formula?

Answer 10

Simplest whole number ratio of the elements in a compound.

Question 10

What is the formula for ppm and where is it useful?

Answer 10

ppm(parts per million)=mass of component/total mass of solution x10^6

Useful in describing very low concentrations.

Question 11

What is an ideal gas?

Answer 11

A gas that obeys gas laws.

Question 12

What is STP and what does it refer to?

Answer 12

STP is standard temperature and pressure
and it refers to 273K (0C) and 100kPa(10^5 Pa).

Question 13

What are isotopes?

Answer 13

Atoms of the same element that differ in their mass number, they have the same amount of protons but different number of neutrons.

Question 14

What is theoretical yield determined by?

Answer 14

The limiting reactant.

Question 14

How do you calculate A(r) - relative atomic mass?

Answer 14

A(r) = weighted average of one atom of the element/ 1/12 mass of one atom of carbon

Question 15

What is the absolute zero temp and what does it mean?

Answer 15

Its 0K and it is the temp where a substance has no kinetic energy, which suggests its the point where all movement of particles ceases.

Question 15

What is a hydrated salt?

Answer 15

Compound containing a fixed ratio of water molecules (water of crystallization) within the crystalline structure of a compound.

Question 16

What is the formula for percentage yield?

Answer 16

percentage yield=experimental yield/theoretical yield x 100%

Question 16

What is the formula for converting a Cp into Cm?

Answer 16

Cm=Cp x d x 100%-1 x M-1

Question 17

What is the ideal gas equation?

Answer 17

PV=nRT
R- universal gas constant = 8.31 JxK-1 x mol-1
P in Pa
V in m3
T in K