Chemistry Lab practicum

If q>0 (positive) that means heat flows___ which does what?

Heat flows in and the object heats up

If q<0 (negative) that means heat flows ___ which does what?

Heat flows out

When heat flows into ice when it melts, but the ice temp is constant during the melting process shows what about the heat flow?

That temperature change does not always accompany heat flow

What is Specific heat, also called Specific Capacity

A measure of a material’s resistance to temperature change

What might make a material more resistant to temperature change?

A greater heat capacity

What is the main purpose of the calorimeter?

to contain the heat transfer between two systems and limit heat exchanged with the surroundings

Without a calorimeter, how might the lab be harder to do?

without it, there would be no way to know how much heat is exchanged with the surroundings, and quantitative relationships like q=mcDT could not be applied

What does enthalpy change (DH) of a reaction represent?

it represents the heat absorbed or released by the reaction under constant pressure

What is colligative properties?

Physical properties that depend on the number of solute particles in solution not the identity of the solute

The freezing point of a pure solvent is ___ than that of a solution

The freezing point of a pure solvent is higher than that of a solution

What would cause a lower freezing point in a solution?

A higher concentrated solution would cause a lower freezing point

The freezing point is directly proportional to what property of a solute

The freezing point is directly proportional to the concentration of the solute.

What are the units for Molality? (m)

It’s moles of solute over kg of solvent

How was freezing point of the solvent and the solution found in the lab?

By averaging out the ten data pts in the flat region of the graph

What does each unit mean in the equation DTf = imKf?

DTf - the freezing point depression of solution due to dissolved solute

i - van’t Hoff factor, represents the number of independent solute particles per unit of whole solute in the solution. The number of solute particles matter not the type of particles, i = 1 for nonelectrolytes

m - molality, special measure of concentration that is independent of temp

Kf - freezing point depression constant that depends on solvent

What is the equation when you have to find the m in DTf = imKf?

m = DTf/Kf

The color we see is a result of wavelengths that ____ and it means _____ is absorbed? What is an example of this?

The color we see is a result of wavelengths that reflected back to our eyes, and it means the complimentary color is what is absorbed. An example of this is when we see green it means green is being reflected and red (its complimentary color) is absorbed.

What does a calibration curve show in a model?

How a dependent variable varies across a range of standard solution