Chemistry 121 Lab Final Test Review
what is the chemical name for baking soda?
what type of chemical is baking soda?
what is the chemical name for vinegar?
What type of chemical is vinegar?
a neutralization reaction occurs when...
an acid reacts with a base to produce water, salt, and sometimes gas.
we can determine the percent yield of a reaction by
dividing the actual yield by the theoretical yield and multiplying by 100
explain what it means when we say the mole ratio of vinegar to baking soda is 1.5:1
its means that the solution will contain 1.5 moles of vinegar and 1 mole of baking soda. there are more moles of vinegar and baking soda is the limiting reactant
explain what is means when we say that the mole ratio of vinegar to baking soda is 1:1.5
it means that the solution will contain one mole of vinegar and 1.5 moles of baking soda. there are more moles of baking soda and vinegar is the limiting reagent
if you react 25.25g of Na2CO3 with 50.0mL of 6.0M HCl, answer the following questions. (molar mass of Na2CO3 = 106.00 g/mol & molar mass of NaCl = 58.45 g/mol)
a.) write a balanced equation
b.) what type of reaction is this?
c.) How many moles of Na2CO3 do you have?
d.) How many moles of HCl do you have?
e.) how many moles of HCl do you need to completely react with 25.25 g of Na2CO3?
f.) What is the limiting reagent? What reagent is in excess?
a.) Na2CO3 + 2HCl yields 2NaCl + H2O + CO2
b.) neutralization reaction
c.) 0.2382 mol Na2CO3
d.) 0.30 mol HCl
e.) 0.4764 mol HCl
f.) limiting = HCl; excess = Na2CO3
1.75g of Ag2O is produced when 3.50 g of Ag reacts with excess O2. What is the percent yield?
4Ag(s) + O2(g) yields 2Ag2O2(s)
What is oxidation?
the loss of electrons
What is reduction?
the gain of electrons
The oxidation number of an atom in a molecule or an ion is defined as...
the charge an atom has or appears to have as determined by the oxidation-reduction rules
An oxidation number can also be called...
an oxidation state
The best way to recognize an oxidation-reduction reaction is...
to see if the oxidation number changes as a result of the chemical reaction
What is the oxidation number of Mg(s)?
What is the oxidation number of H2(g)?
The algebraic sum of the oxidation numbers for the atoms of a neutral compound must be...
In a polyatomic ion, the sum of the oxidation number must be equal to...
the ion charge
What is the oxidation number of C in CO?
What is the oxidation number of C in CO3 2-?
What is the oxidation state of fluorine when combined with another element?
The compound Ca(NO3)2 has ______ calcium atom, _______ nitrogen atoms, and ________ oxygen atoms.
1 calcium, 2 nitrogen, & 6 oxygen
In the compound Ca(NO3)2 for each mole of calcium ions there are ______ moles of nitrate ions and the mole ratio of calcium to nitrate ions is _______.
What is a hydrate?
a compound that has water molecules loosely attached that can be removed by heating.
When the aluminum wire was placed in the solution of the copper ions, what was oxidized?
When the aluminum wire was placed in the solution of copper ions, what was reduced?
Cu 2+ (aq)
When the aluminum wire was placed in the solution of copper ions, what was the oxidizing agent?
Cu 2+ (aq)
When the aluminum wire was placed in the solution of copper ions, what was the reducing agent?
Why was an analytical balance used in the aluminum wire experiment?
because it is more accurate and can generate more sigfigs than the top loading balance
How was the top loading balance used in the aluminum wire experiment?
it was used to place slightly more than 1 gram of the unknown hydrate into the crucible
Why was the Buchner funnel used in the aluminum wire experiment?
it was used to quickly filter the copper out of the solution that was made
what is ethanol?
why was ethanol added to the copper during filtering?
because it helps to dry the filter paper out because it has a lower boiling point than water
What is the entire name of 6M HCl
6 molar of hydrochloric acid
How did the temperature of the solution change when the wire was added?
Thermodynamically what type of reaction does an increase in temperature indicate?
the measurement of the exact volume of a solution of known concentration that is required to react with a measured amount of an unknown substance or solution
What is a standard solution?
a solution of known concentration
How is a primary solution made?
from a solid substance by accurately weighing the solid to four or more significant figures on the analytical balance. then the solid is added to a volumetric flask and diluted with distilled water to get a solution of known molarity.
A primary solution is made from a liquid by...
using a volumetric pipet to measure precise amounts of the liquid and then diluting in a volumetric flask
Because NaOH absorbs carbon] [dioxide and water from the air, it cannot be weighed accurately. Therefore, it cannot...
be a primary standard
After it has been standardized, the exact molarity of the NaOH is known & it can be...
used to standardize an unknown acid solution
Potassium hydrogen phthalate
a primary standard that can be used to standardize NaOH solutions
How many moles are needed to titrate one mole of KHC8H4O4?
Which acid-base indicator will be used in the experiment?
What is the color change in the acid-base reaction?
colorless to pink
We end the titration when...
one drop of the titrant causes the indicator to change color & the color stays for 30 seconds
The indicator color change indicates...
the end point of the titration and tells us the reaction is complete.
Know how to standardize HCl
Why wasn't it necessary to dry the Erlenmeyer flasks between samples in the standardization of HCl experiment?
you do not have to dry the flask because you are measuring a definite amount of acid into the flask for each trial & your calculations are based on the exact quantity of acid being added to the flask from the syringe. Therefore, the flask can contain distilled water or distilled water can be added without affecting the experiment
What mass of KHC8H4O4 would be neutralized by 25.25mL of 0.1034 M NaOH?
0.5332 g KHC8H4O4
How many mL of 0.1022 M NaOH are needed to neutralize 5.00 mL of a 0.1152M HCl solution?
a form of energy called thermal energy which can pass from an object at high temperature to an object at a lower temperature.
A calorimeter is...
a/an insulated container made so that no heat is lost from the container during the experiment
Styrofoam cups are used in this experiment because...
they are good insulators and relatively inexpensive
q H2O means...
the change in temperature of the water
C H2O means...
the specific heat of water
m H2O means...
the mass of water
delta t means....
the quantity of the heat of the water
Specific heat is...
the amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius
amounts of heat are measured in either...
[joules] or [calories].
the specific heat of water is...
4.18 joules/g(degrees celsius)
the boiling point is...
when the liquid molecules get enough energy from the added heat that they form vapor
Liquid boils when...
the vapor pressure = the atmospheric pressure
what is inside of the bubbles of a boiling liquid?
the gaseous liquid that is boiling
since atmospheric pressure decreases with increasing elevation, the water has a ....
lower boiling point at higher elevations
explain why the temperature of boiling water can be different on different days even if the elevation is the same
Air pressure changes when different weather fronts move through an area. The fronts cause changes in air pressures (highs and lows). Therefore, the temperature of boiling water can be different on different days even if the elevation is the same
the heat flow of reactions at constant pressure
if the temperature of the water in the calorimeter increases, then...
heat has been given off by the reaction mixture
If heat is given off by the reaction, then the reaction is _________. Therefore q H2O is ________ & enthalpy is _________.
exothermic, positive, & negative
Using what you learned about specific heat in lab, explain why an empty metal pan on a stove heats much faster than the same pan filled with water.
an empty metal pan on the stove heats much faster then the same pan filled with water because the metal pan has a much lower specific heat compared to water so it takes less time to heat.
Explain why your car overheats if your fan belt breaks
if your fan belt breaks there is no more air flowing through to cool the liquid that is absorbing the heat from the engine of the car.
explain why your car overheats if your radiator has a hole in it
your car would overheat if your radiator had a hole in it because all of the water would run out of the radiator so there would be no water flowing through the engine to absorb the heat, thus the car would overheat
delta t =
a change in temp.
how is delta t calculated?
by subtracting the final temp. minus that initial temp.
what is the chemical name of CaCl2?
Why is CaCl2 often used in the winter to melt ice?
because when it is mixed with water (ice) the reaction is exothermic, thus the ice is melted & less dangerous
Charles Law states that....
at constant pressure the volume of a given gas is directly proportional to its Kelvin temperature
The objective of this experiment is to verify Charles Law by finding ...
the volume occupied by a gas at 2 different temperatures.
Charles law is verified if...
the volume-to-temperature ratios are close to the same number
Boyle's Law states that....
the volume of a fixed amount of gas at a constant temperature is inversely proportional to the pressure exerted on the gas
We will verify Boyle's Law by...
using a syringe that has a trapped column of gas and apply weights to increase pressure
Avogadro's Law states that...
the volume of a gas at constant temperature and pressure is directly proportional to the quantity of the gas
As you put more moles of air into a balloon the volume...
Amonton's Law states...
at a constant volume and quantity, the Kelvin temperature and pressure of a gas are directly proportional
the combination of all the gas laws is the...
Ideal gas law
the equation of the Ideal gas law is
PV = nRT
standard temperature and pressure
STP is defined as...
0C and 1 atm.
Molar volume of an ideal gas at STP is
Two 125mL _________ flasks will be used in the Charle's Law experiment
What 2 types of clamps will be used in the Charles Law experiment?
Utility and screw clamps.
Closing the ______ clamp could cause the flask to _____ as the air expands
screw ; explode
Use the ______ clamp to remove the flask from the ________ water
utility ; boiling
When the flask is submerged in the cooling bath, check to make sure the rubber tubing ______ completely and the end of the tubing stays ______ the surface of the water.
opens ; below
The volume of the water in the 250mL graduated cylinder = volume of the _________ = volume of hot ________
flask ; air
Charles Law is proved if the difference of the k value is less than _____
The Boyle's Law apparatus that is on your table has a ______ with a trapped column of air and a piece of _______ on top which is where you will put the weights
syringe ; wood
the weights in this experiment are ________
since the bricks are too heavy to weigh on the balances in the lab, they have all been ______ and ______ for you.
numbered & weighed
The Boyle's law apparatus is not perfect because there is ________ between the ________ and the ______ of the syringe
friction between the plunger & sides
Write the equation used to calculate % yield
(actual yield / theoretical yield) X 100
The reaction represented on page 109 is exothermic because...
; the products have less energy than the reactants
Chemists often use models made of balls and sticks or straws to represent...
atoms & bonds
Models are useful in visualizing the arrangements of atoms & bonds in these structures because...
molecules & atoms cannot be seen with the human eye
The atomic theory states...
that the chemical & physical properties of a substance are determined by the distribution of valance electrons and by the arrangement of the atoms in the molecule
A lewis structure is a...
two dimensional representation of a molecule or ion that shows the atomic symbols of the elements and dots or lines to represent electrons that are either in bonds or are unshared
The first step in drawing a Lewis structure is to...
determine the number of valance electrons
the ability of an atom to attract ions to itself
What is the most electronegative element?
If an atom does not obey the octet rule how many valance electrons does it have?
more than 8
Using the chart on page 121, what is the molecular geometry of a substance with the general formula of AX3E?
The general rule for bond length is...
that single bonds are the longest, double bonds are shorter, and triple bonds are the shortest of the 3 types
when compounds have more than one possible Lewis structure, these structures are called...
formal charge of an atom is defined as...
the total number of [valance] electrons of that atom minus the number of valance electrons it [owns] in the molecule: it owns [all] its unshared valance electrons and [half] of itâs shared valance electrons.