Test on Thursday, December 1, 2016 Flashcards
What does Accuracy mean? 3
It refers to how close the measurement is to the true value
Determined by the procedure used to obtain measurement
Improper method results in all values consistently too high or too low
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For example: A dart board
Accuracy — I get most of my darts around the centre. Not necessarily close together
Precision — All my throws land in the exact same area (whether or not it is close to the center)
What are the three types of errors?
Random error
Systematic error
Gross error
Define Anhydrous salt
When hydrates release water
Give two examples on random error.
Uncertainty of measuring a liquid
Uncertainty of measuring mass
What is L equal to? Also called Avogadro’s number
6.022×10²³
What does STP mean? 3
It stands for Standard Temperature and Pressure
Standard Pressure is 100 kPa
Standard Temperature is 0°C
How can Random error be reduced?
It can be reduced through repeated measure as it alters measurements equally on both sides of a value
Define Gross error.
Recognized one time mistakes including spills, mislabeling and recording wrong value
How do you calculate percent yield?
(Experimental yield/theoretical yield) * 100
Define Formula Mass 1
Is the sum of the atomic mass of each ion in the empirical formula
(Used for ionic compounds)
k2O has 2 potassium and 1 oxygen
FM = 2(29.10g/mol)+(116.00g/mol)
FM = 74.2
How many volume does one mol of any gas occupy at STP?
22.7 L
Define Precision. 2
It refers to how close several measurements of the same quantity are to each other
It is determined by the device used to measure
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A graduated cylinder is more precise than a beaker for volume because its uncertainty is +- 0.5ml
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For example: A dart board
Accuracy — I get most of my darts around the centre. Not necessarily close together
Precision — All my throws land in the exact same area (whether or not it is close to the center)
What do Chemical Reactions require? 3-6
New substances to be formed
Bonds of reactants to be broken and bonds of products to be formed
Results in an energy change (gain or loss)
Fixed ratios between reactants/products
Ratio in number of moles or particles
Called stoichiometry
Give two examples of desiccants.
“Dry it” bag contains anhydrous calcium chloride to dehumidify the air
Silica gel is found in packages of many electronic devices
Define Desiccant.
Anhydrous salts that will attract water out of the air to reform hydrate
Define Molar Mass
A single atom has a very small mass
What element and its isotope are all the masses given in the periodic table based on?
It is based on the isotope carbon-12
What is mole or Avogadro’s number used for? 4 or 2
A very big number useful for counting small things like:
Atoms
Molecules
Ions
Formula Units
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Mainly Converting from # of atoms to moles
and
Converting from # of moles to atoms
Define Systematic error
Inherent in procedure and unnoticed in lab
What is 22.7 L written as also? (how it is written in IB)
22.7 dm³
What is the symbol of the molecular mass? (It is the same as Relative Atomic Mass)
Mr (the r is a subscript)
What are Quantitative data? 2
Data from observations from sight, touch, taste, hearing and smell
May be prediction of unknown values or determination of slope of line or curve
Define Molecular Mass 1
Is the sum of the atomic mass of each atom in the molecule
H2O has 2 hydrogen and 1 oxygen
MM = 2(1.01g/mol) + 1(16.00g/mol)
MM = 18.02
Where are the three errors addressed, in what section?
The Evaluation section
Define Atomic Mass
Weighted mean of all the isotopes of the element
Measure in grams per mole
Atomic mass of carbon-12 is 12.01 g/mol
What are proper techniques that need to be used to reduce Systematic errors? 4
Measured from bottom of meniscus
Calibrated measuring devices (Tareing)
Properly prepared solution
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It is possible to have several precise readings taht are inaccurate
Like having a misaligned scope on a gun
Define Structural Formula for Chemical formulas
Is shows structure like 3D diagrams from VSEPR
What is the symbol of the relative atomic mass?
Ar (the r is a subscript)
What are Qualitative data? 2
Variables are proportional, inversely proportional
Data is obtained from instruments
What are metal ions chemically bonded to water molecules called?
Hydrated ions
Why must anhydrous salts be stored in sealed containers?
To prevent moisture absorption
What does the term Molar Mass be used for? What type of masses? 3
Atomic mass,
Atomic mass,
and Formula mass
Define Empirical Formula for Chemical formulas
Lowest whole number ratio of atoms of each element in a substance
Ex. NaCl
Define Stoichiometry
The relationship between the relative quantities of substances taking part in a reaction or forming a compound, typically a ratio of whole integers.
What does the single arrow in a Chemical word equation mean? 2
“Yields”
Reaction goes to completion
What is a Chemical (Word) Equation? 5
A chemical “sentence” that has:
Reactants on the left
Names or formulas of initial substances
Single-headed arrow means “yields”
Reaction goes to completion
Products on the right
Names or formulas of final substances
Quantities of each substance for complete reaction(Not for word equations)
Coefficients in front of fromulas
State symbols (Not for word equations)
Solid (s), liquid (l), gaseous (g) or dissolved in water/aqueous (aq)
Define Molecular Formula for Chemical formulas
Shows actual number of atoms of each element for a molecule
Ex. CH2O
