Chem Lab Final

all the following are substances that can sublime except

SiO2

In a particular gravimetric analysis, the precipitate of barium sulfate was weighed before it was completely dried. The likely impact of this error on the calculated result is

a higher result than the correct value.

The effect of the presence of excessive amounts of mineral acids in the gravimetric determination of sulfate is...

a lower result than the correct value

saturated

a solution that contains the maximum amount of dissolved solid

unsaturated

a solution with less than the maximum amount of dissolved

what is the law of definite proportions?

a statement that every chemical compound contains a fixed constant proportions (by mass) of its constituent elements.

define the term compound

a substance formed when two or more chemical elements are chemically bonded together.

Define metathesis reaction

an exchange of ions between two molecules during a reaction. NaCl+CuS-> CuCl + NaS

suggest a way to determine whether a colorless liquid is pure water or salt solution without tasting it

boil the water all the way to see if there is residue left

from what substances can esters prepared?

carbocylic acids with alcohols in the presence of a catalytic amount of inorganic acid.

the substances making up a mixture are called

components

how do decantation and filtration differ? which should be faster?

decantation is when the liquid of a mixture is gently poured away from a solid while filtration is when liquid is poured into a filter and the solid is left in the filter. Decantation should be faster.

what are meant by the terms decantation and filtration

decantation: pour off solvent leaving behind precipitate filtration: pass through filter that separates our components of a mixture difference in particle size

in disposing off waste in the laboratory, the waste is

disposed off in the appropriate container in the waste hood

A pipette is used to transfer a base into a flask sitting under a burette filled with acid. The pipette, the flask and the burrette should, respectively be rinsed with.

distilled water, base and acid

What are esters? what is their general structure?

esters are derivatives of organic acids. R-C-OR () O

give criteria in terms of temperature changes for exothermic and endothermic reactions

exothermic reaction: release heat, endothermic reaction: absorbs heat

Heterogeneous mixtures are also called solutions true or false

false

distilled water is added to the reaction mixture to decompose any anhydride remaining. true or false

false

the lowest mass the top loader balance can record to is 0.0001g true or false

false

what is a precipitate?

formation of a solid from liquid solution

what observations might you make that suggest that a chemical reaction has occurred?

gases are produced, precipitants are formed or color changes occur.

Why do you calibrate thermometers and pipets?

helps with accuracy of your results. It mayb not be accurate due to human error which can hurt your results.

When will reactions proceed to completion?

in metathesis reaction proceed to completion whenever one of the products is removed from the solution. such as in the formation of a gas or an insoluble substance.

Why should you never place a hot object on the pan of a balance?

it may damage the balance and also cause the air pressure around the pan to fluctuate and make it harder to set the accurate measurement

define the term limiting agent

limiting agent in a reaction is the agent that would be used up completely if the reaction went to 100% completion

what are the basic units of length, mass, volume, and temperature in the SI system?

mass = kg, volume = cubic meter (m^3), temperature = Kelvin (K), length = meters

the SI unit for length is

meters

what distinguishes a mixture from an impure substance?

mixture is two or more pure substances. impure is one substance contaminated by other small amounts of substances.

how do empirical and molecular formulas differ?

molecular formula: chemical formula that indicate the actual numbers and types of atoms in a molecule. empirical formula: chemical formula that indicate relative numbers of atoms of a type.

always pour water into acid yes or no?

no

Define limiting reagent

reactant that is completely used up in a reaction. It limits/determines how much product is formed.

give one example of homogeneous mixture

salt water

supersaturated

solutions that contain more than the amount of solute before a saturated solution

List three methods of separation

sublimation, decantation, filtration

Before you can write a chemical equation, what must you know?

the molecular formula of reactants and their number of number of charges so that you can write a balanced chemical equation between products and reactants. the products must be established.

define percent yield in general terms

the percent yield is expressed as the ratio of the recovered mass to initial mass, multiplied by 100

Decantation

the process of separating a liquid from a solid (sediment) by gently pouring the liquid from the solid so as not to disturb the solid is called

what is the role of inorganic acids in the esterification process?

they are the catalyst to create a reaction with carboxylic acids

what is one physical property of esters?

they have pleasant, fruit like odors

what is the process of recrystallization?

to remove phenolic impurities

most common thermometers use mercury or colored alcohol as the liquid true or false

true

a solution with less than the maximum amount of dissolved solid is

unsaturated

the best procedure to use when filtering an aqueous solution to collect a precipitate is to

wash the precipitate with a minimal amount of water

Define process of sublimation

when a solid passed directly into the gaseous state without the appearance of the liquid state.

How do you know all the sulfur is burned off when reacting with zinc?

when the vapor from the compound has dissipated and cannot be seen anymore. It leaves behind a white yellowish powder.

What is the density formula

D=mass/volume

the process of a solid and a solvent forming a solution is termed

dissolution

How to find the pH of a M solution

find the -log of the Molarity

what is the role of inorganic acid in the esterification process?

it is to act as a catalyst for esterification process

what is precision

the reproducibility of a set of results

What is the carboxylic acid group?

-C-OH () O

the correct record in an analytical balance

0.0000

describe a test for phenols

1% FeCl3 solution is employed as a test for presence of phenols

Why should you never determine the mass of a hot object?

1. Because it is unsafe 2. hot objects will radiate heat in the form of convection currents, making slight changes in the readings.

what is the maximum percent yield in any reaction

100%

3.70L is what volume?

3700ml and .0037cm

Name two liquids that are flammable in this experiment

Acetone and methanol

List three physical properties of substances.

Color, Smell, Density

All substances are soluble in water. True or false.

False

what decimal power does M represent?

Mega

why is it necessary to calibrate a thermometer and volumetric glassware?

It is necessary to standardize values and ensure the instrument works properly