Answer:
SYMBOLS, FORMULAS AND MOLAR MASSES
OBJECTIVES
1. To correctly write and interpret chemical formulas
2. To calculate molecular weights from chemical formulas
3. To calculate moles from grams using chemical formulas
INTRODUCTION
Part I. Symbols and formulas
An element is a homogeneous pure substance made up of identical atoms. All matter is made
up of elements and, since chemistry is the study of matter, it is convenient to use symbols to represent
the elements rather than using the entire name.
By international agreement, specific symbols are assigned to each element (Note: This means
that while names of the elements vary with language, symbols are constant throughout the world.) Each
element is assigned a one- or two-letter symbol. The first letter is capitalized, the second (if there is
one) is not. While this often seems trivial, it is in fact a very important point. For example, in chemical
language Co represents cobalt, which is a metal and an element, while CO represents carbon monoxide,
a compound which is a colorless, odorless gas! Even when there is not an obvious correspondence,
for instance "MN", it can cause confusion. Do you mean the element manganese? Did you forget a
letter and mean something else? Are you using "M" to represent something else entirely? Chemists
sometimes use "M" to represent any metal. It is well worth the trouble to memorize the symbols for
common elements.
Since compounds consist of elements, the chemical formulas of compounds also consist of
elements with subscripts used to denote the number of atoms per molecule. If there is no subscript, it is
implied that there is one of that kind of atom. Ones never appear in chemical formulas. Not only do
subscripts denote ratios of atoms, they also denote the ratio of moles of element to one mole of
compound. Parentheses can be used to show groups of atoms, with the subscripts showing how many
groups there are. Parentheses are not used if there is only one group.
Examples: For one mole of the following compounds, how many moles of each element are
present?
MgCl2 1 mole Mg, 2 moles Cl
Mg(NO3)2 1 mole Mg, 2 moles N, 6 moles O
NaNO3 1 mole Na, 1 mole N, 3 mole O
AgCl 1 mole Ag, 1 mole ClPart II. Molar Masses
Each atom has a different size and therefore a different mass. The relative masses of each
element can be found on the periodic table. For example, one atom of magnesium weighs 24.31 amu
(atomic mass units). However, one mole of magnesium weighs 24.31 g. (Moles were planned that
way!) Since one mole of MgCl2 consists of one mole of magnesium and two moles of chlorine, the
mass of one mole of MgCl2 must be the sum of the masses of the elements. The mass of one mole of a
substance is called the molar mass or molecular weight.
Examples: What is the molar mass of the following compounds?
MgCl2 24.31 + 2(35.45) = 95.21 g/mol
Mg(NO3)2 24.31 + 2(14.01) + 6(16.00) = 148.33 g/mol
NaNO3 23.00 + 14.01 + 3(16.00) = 85.01 g/mol
AgCl 107.9 + 35.45 = 143.4 g/mol
(Note: Yes! You DO have to count significant figures when calculating molecular weight/molar
mass. However, the number of significant figures may vary depending on which periodic table you use.)
Chemists are generally interested in number of moles. Unfortunately, it is impossible to measure
moles directly. However, masses are easily measured, and if the chemical formula of the compound is
known, the molar mass can be used to determine the number of moles. The molar mass is defined as:
molar mass = grams/moles = g/mol (1)
Moles may be calculated by using molar mass as a conversion factor in dimensional analysis where
molar mass in grams = 1 (exactly) mole of compound (2)
This method is used in multi-step calculations. For example, if 0.873 g of MgCl2 is weighed out, it
is 9.17 x 10-3
moles.
1 mole
0.873g x 95.21 g = 9.17 x 10-3
mol MgCl2 (3)
However, 0.873 g of AgCl is only 6.09 x 10-3
mol.
1 mole
0.873g x 143.4 g = 6.09 x 10-3
mol AgCl (4)Molar mass may also be used to relate moles to grams. For example, 0.158 mol of MgCl2 is 15.2 g.
0.158 mol x 95.21 g = 15.2 g MgCl2 (5)
1 mol
Percent is used to express parts per one hundred. Usually in chemistry, it refers to
g of species of interest x 100 = % (6)
g of whole thing
Example: For the % Mg in MgCl2: In one mole of MgCl2, there are 24.31 g of Mg (molar mass of Mg,
the part we are interested in) and 95.21 g of MgCl2 (the whole thing), so %Mg in MgCl2 is
(24.31/95.21) x 100 = 25.53% Mg (7)
PROCEDURE
Work individually.
The formula for calcium phosphate is Ca3(PO4)2. Weigh about 2 g of calcium phosphate to the
nearest 0.001 g. In other words, you do not have to have exactly 2.000g, but you must know the
weight you have exactly. Acceptable results include but are not limited to: 1.985g , 2.035g, 2.314g
etc.
Be sure to report all results with the correct number of significant figures and appropriate units!
A doctor prescribes 125 mg of penicillan to be taken 4 times each day. The
concentration of the solution given to the patient is 250mg penicillan/5ml. How
many mL should the patient take in each dose?
1) 500 mL
2) 10.0 mL
3) 2.50mL
4) 50.0 mL
5) 2.0 mL
10 ml should the patient take in each dose
Further explanationGiven
125 mg of penicillan ⇒ 4 times/day
The concentration = 250 mg/5 ml
Required
The volume of the dose
Solution
The mass of penicillan/day :
= 125 mg x 4 times
= 500 mg
The volume/day :
= 500 mg : 250 mg/5 ml
= 10 ml
The area of a telescope lens is 6.668 × 103 mm2. What is the area in square feet (ft2)? Enter your answer in scientific notation
Answer:
[tex]7.13\times 10^{-2}\ ft^2[/tex]
Explanation:
The area of a telescope lens is 6.668 × 10³ mm²
We need to convert the area in ft².
We know that,
[tex]1\ mm^2=1.07\times 10^{-5}\ ft^2[/tex]
It means,
[tex]6.668 \times 10^3\ mm^2=6.668 \times 10^3\times 1.07\times 10^{-5}\ ft^2\\\\=0.0713\ ft^2[/tex]
or
[tex]0.0713\ ft^2=7.13\times 10^{-2}\ ft^2[/tex]
So, the required answer is [tex]7.13\times 10^{-2}\ ft^2[/tex].
sodium hydrogen carbonate is heated after heating which substance is form??? and what is the colour of the substance
What valence electron number do they all have in common
23.When an atom absorbs energy
a.One or more electrons will move to a higher energy orbit
b.One or more electrons will move to a lower energy orbit
c.Colored light is produced
d.There is an explosion
Answer:
a.One or more electrons will move to a higher energy orbit
Explanation:
Absorbing energy means that the electron gets excited and jumps to a higher level.
Highlight the examples of radiation in the passage
below.
A chemist working in the laboratory is
investigating the thermal energy of H2O in a
solid, liquid, and gas state. First, she places
ice in a pan on a burner and heats it. She
records the temperature at which the solid ice
melts. Next she takes the liquid water and
heats it in a microwave. The liquid begins to
bubble and evaporate into a gas. She records
the temperature at which the liquid water
turned into a gas.
Answer:
Heating of the liquid water in a microwave.
Explanation:
Radiation is a form of heat transfer process that does not require a material medium rather it travels through space or vacuum in the form of electromagnetic waves or radiation. Heat transfer by radiation occurs in the form of microwaves, infrared radiation, visible light, or another form of electromagnetic radiation is emitted or absorbed. Some common examples of heat transfer by radiation is the warming of the Earth by the Sun, the warmth one experiences while sitting by the campfire, or the heating up of foods in a microwave.
Black bodies or surfaces are good absorbers as well as emitters of radiation. On the other shiny or white surfaces are poor radiators of heat.
From the above discussion on radiation, it can be seen that when the chemist takes the liquid and heats it in a microwave, the heat absorbed by the liquid to change to gaseous state is transferred through radiation.
When an electron in an atom moves from high to low
energy levels:
a alpha particles are emitted
b gamma rays are emitted
c energy is emitted as electromagnetic radiation
d energy is absorbed
Answer:energy is emitted as electromagnetic radiy
Explanation:
3. When two atoms are combined what do they make?
Answer:
When two or more atoms chemically bond together, they form a molecule. Sometimes the atoms are all from the same element. For example, when three oxygen atoms bond together, they form a molecule of ozone (O3). If a molecule forms from atoms of two or more different elements, we call it a compound.
Explanation:
PLEASE MARK ME AS BRAINLIEST
acid+base->salt+water
What type of reaction is this?
Answer:
The reaction of an acid with a base is called a neutralization reaction. The products of this reaction are a salt and water.
Answer:
Neutralization reaction
Explanation:
Neutralization reaction it the reaction of acids and bases that form salt and water
hope it's helpful ❤❤❤❤
THANK YOU.
An elephant and a parakeet standing on ledge will have a different amount of potential energy because of their . this is for science actually
Answer:
Mass
Explanation:
What type of chemical reaction is the following reaction:
carbon monoxide and oxygen yield carbon dioxide
Answer:
decomposition reaction
Carbon Tetrahydride reacts with Oxygen gas to form Carbon Dioxide gas and Dihydrogen Monoxide gas.
Explanation:
Which formula represents a
polar molecule
containing polar covalent bonds?
A. H2O
B. CO2
C. NaCL
D. Cl2
Answer:
A. H2O
Explanation:
Let us first define the three types of bonds:
1. Nonpolar Covalent: electronegativity difference < 0.4
2. Polar Covalent: electronegativity difference between 0.4 and 1.8
3. Ionic: electronegativity difference > 1.8
This will help us eliminate choices C and D:
-NaCl has a electronegativity difference of 3.0 - 0.9 = 2.1 (ionic bond)
-Cl2 has a electronegativity difference of 3.0 - 3.0 = 0 (nonpolar covalent bond)
However, we still have two more options, A and B, but they are not diatomic for us to use the electronegativity differences with.
We must now consult their geometries. Because CO2 has a linear geometry (O=C=O), the two sides will cancel each other out, resulting in a nonpolar covalent bond. At this point, by process of elimination, we can already determine the answer to be A. H2O. We can verify this by looking at the geometry of H2O, which is bent (H-O-H; imagine the O is above the H's, I cannot draw it in this response). H2O's bent geometry classifies it as polar covalent; the electrons are slightly more attracted towards the O, the more electronegative element. Side note: this makes the O slightly more negative in charge, whilst the H's are slightly more positive in charge.
P.S. I apologize for not being able to draw and demonstrate that last paragraph, but I hope you get a general idea. You can search up the "H2O geometry" and "CO2 geometry" to get a better idea! :)
H₂O represents a nonpolar molecule containing polar covalent bonds. Hence Option (A) is correct
What is Polar Covalent Bond ?A polar covalent bond exists when atoms with different electronegativities share electrons in a covalent bond.
Consider the hydrogen chloride (HCl) molecule. Each atom in HCl requires one more electron to form an inert gas electron configuration.
Water (H₂O), like hydrogen Chloride (HCl), is a polar covalent molecule. When we look at a diagram of water , we can see that the two hydrogen atoms are not evenly distributed around the oxygen atom
Water (H₂O) is polar because of the bent shape of the molecule. The shape means most of the negative charge from the oxygen on side of the molecule and the positive charge of the hydrogen atoms is on the other side of the molecule.Thus, This is an example of polar covalent chemical bonding.
Therefore, H₂O represents a nonpolar molecule containing polar covalent bonds. Hence Option (A) is correct
Learn more about bonding here :
brainly.com/question/1603987
#SPJ2
What would be the most likely explanation if none of the tested paint samples had turned brown?
1. The reaction was not actually caused by UV light.
2. The reaction only happens in real sunlight, not artificial.
3. The paint behaves differently on a canvas than it does in a laboratory.
4. None of the tested mixtures matched the chemical composition of Van Goghs paint.
Answer:4/d
Explanation:
i did this before
Helppp me plzzzzz!!!
Answer:
they use echos to communicate
Explanation: dolphins make echos in order to signal there partners, and others in there pod. or they can use it to signal for prey, or signal that they are in trouble.
Answer: A good example for this one is bats.
Explanation: While a couple of bats are known to emanate the beats through their nose, most bats will in general express them. The recurrence is estimated to be around 200 heartbeats each second, nonetheless, the time frame can fluctuate with the types of a bat. Credits: Adi Ciurea/Shutterstock A bat's squeaks are more rewarding than Ben's on the grounds that with higher recurrence comes higher-goal or more distinctive detail – they are equipped for evading deterrents no more extensive than a human hair! They use it to find and explore towards prey, for example, a hurrying bug. As the distinguished sound waves that structure the pictures are basically echoes, they should adjust to a standard — the recovered train of heartbeats should be sufficiently noisy to get back to the sender, yet short sufficient with the end goal that the reverberation of the sender returns before the following one withdraw.
Hey can someone please help me with this
Answer:
This is not a redox reaction.
Explanation:
A redox reaction is a reaction that involves reduction and oxidation processes. The best way to identify a redox reaction. Changes in the oxidation number f the species indicates that it is a redox reaction.
Na+
Reactant side = +1, Product Side = +1; No change
Cl-
Reactant side = -1, Product Side = -1; No change
Ag+
Reactant side = +1, Product Side = +1; No change
N
Reactant side = +5, Product Side = +5; No change
O
Reactant side = -2, Product Side = -2; No change
There is no change in any of the oxidation numbers, Hence this is not a redox reaction.
How did modern scientists experiment with Van Gogh's paints to determine their chemical reactions?
1. They used X-ray analysis.
2. They used litmus testing.
3. They burned the paint to examine what elements were left after the chromium was burned off.
4. They studied the density of modern yellow paint to that of 100-year-old paint.
Answer:
I think the answer is A - they used X-ray analysis.
Explanation:
Answer:They used X-ray analysis
Explanation:
It’s in the text
Give 2 reasons why is copper used for electrial wires
Answer:
Copper electrical wires are safer to use than wires made of most other conductive metals because they are resistant to heat. As you can see, copper is the preferred metal for electrical wires for several reasons. It has high electrical conductive; it's inexpensive; it's ductile; and it's thermal resistant.
Electrical energy is the amount of energy that an object contains due to kinetic energy
Answer:
The energy an object has due to its motion is called kinetic energy. Factors Affecting Kinetic Energy: the kinetic energy of an object depends on both its speed and its mass. The faster an object moves, the more kinetic energy it has.
Explanation:
PLEASE HELP
which of the following has the smallest ionic radii?
1. K
2.Na
3.Ca
4.Mg
Answer:
sodium, Na
Explanation:
Na, is the smallest with atomic number 11 and it has one valence electron
How many moles of ammonia gas are produced from 3.6 moles of hydrogen gas and excess nitrogen gas?
Answer:
If so, the limiting reagent of Nitrogen would allow 16 moles of Ammonia to be produced.
Explanation:
CAN SOMEONE PLZ HELP ME ON THIS
Answer:
Q1. C
Q2.ring number 1 is 2
ring number 2 is 8 and
ring number 3 is 18
Q3. p can contain 6 electrons max
and d can contain 10 electrons max
Q4. D
What is the total magnification if we using objective lens 4x and our eyepiece (ocular) lens is 10x
40x
100x
400x
1000x
You're invited to a hot tub party! Being the science geek that you are, you decide to calculate the amount of mL in the 650.0 gallon hot tub!
Answer:
cool but can we have a little bit bigger
Explanation:
(NH4)2SO4. How many N are there?
Calculate the vapor pressure (in torr) of a 35°C solution of ethanol and propanol where the mole fraction of propanol is .75.
Assume ideal behavior.
P°ethanol = 100 torr
P°propanol = 36 torr
Answer:
i wish i know
Explanation:
how does plants react with no scratch?
Answer:
You see, plants need energy to grow and grow and grow. They use energy from sunlight to make a simple sugar, glucose. Whenever the plant needs energy, it can chomp a little glucose off of the starch.
without energy it wont get energy/food so it will eventually die
Explanation:
Scott and his classmates were looking at an animal cell under a microscope. They are trying to locate the cell's DNA, which is found in its chromosomes. Where should Scott look to find the chromosomes?
In the mitochondria
In the cell nucleus
In the cytoplasm
In the cell vacuole
what is the answer PLEASE HELP!!
Answer:
the water displaced will not help the student find the correct volume because you can not accurately calculate it. you have to get the water when it is settled then you place the wood in.
Explanation:
What is the oxidation number for Cl?
2
+1
-1
+2.
Answer:
-1
Explanation:
Questions and answer options are on ( Picture )
remember pick 2 answers it says
help :(
ZOOM IN if needed
Answer:
The answer is A
Explanation:
I dont see any claim
