B. silver tarnishing
A 0.500-g sample containing Na2CO3 plus inert matter is analyzed by adding 50.0 mL of 0.100 M HCl, a slight excess, boiling to remove CO2, and then back-titrating the excess acid with 0.100 M NaOH. If 5.6 mL NaOH is required for the back-titration, what is the percent Na2CO3 in the sample?
The percentage by mass of Na2CO3 in the sample is 48%.
The equation of the reaction of Na2CO3 with HCl;
Na2CO3(aq) + 2HCl(aq) ------> 2NaCl(aq) + H2O(l) + CO2(g)
Since the HCl is in excess, the excess is back titrated with NaOH as follows;
NaOH (aq) + HCl(aq) ---->NaCl(aq) + H2O(l)
Number of moles of HCl added = 0.100 M × 50/1000 L = 0.005 moles
Number of moles of NaOH added = 5.6/1000 × 0.100 M = 0.00056 moles
Since the reaction of NaOH and NaOH is 1:1, 0.00056 moles of HCl reacted with excess HCl.
Amount of HCl that reacted with Na2CO3 = 0.005 moles - 0.00056 moles = 0.0044 moles
Now;
1 mole of Na2CO3 reacts with 2 moles of HCl
x moles of Na2CO3 reacts with 0.0044 moles of HCl
x = 1 mole × 0.0044 moles / 2 moles
x = 0.0022 moles
Mass of Na2CO3 reacted = 0.0022 moles × 106 g/mol = 0.24 g
Percentage of Na2CO3 in the sample = 0.24 g/ 0.500-g × 100/1 = 48%
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Dentists use a soft, clay-like material to make a filling for a cavity. The filling stays soft under the light of the dentist’s lamp, but it hardens when the dentist shines an ultraviolet flashlight on it. Why does light from the ultraviolet flashlight harden the filling when light from the lamp does not?
Answer:
the clay will be melted by the light
Explanation:
because UV rays are hot but in a way, human skin can not feal pain
Many fundamental concepts are at the heart of chemistry. Match the description to the name.
Answer:
you dony have a picture for me to match them
Explanation:
Why does the Hubble Space Telescope take clearer pictures than other telescopes?
Answer:
Space-based telescopes like Hubble get a much clearer view of the universe than most of their ground-based counterparts. ... Ground-based telescopes can't do the same, because the Earth's atmosphere absorbs a lot of the infrared and ultraviolet light that passes through it.
Apply Concepts
6. Describe the ecosystem in the picture.
the size of camphor kept in store house gradually decrease in size after few а days?
Answer:
Because it goes through the process of sublimation.
Explanation:
what are the solar home lighting
Answer:
Sunlight
Explanation:
Home lighting System is powered by solar energy using solar cells that convert solar energy (sunlight) directly to electricity. The electricity is stored in batteries and used for the purpose of lighting whenever required
Calculate the vapor pressure in torr of a solution containng 24.5 g of glycerin (C3H8O3) in 135 mL water at 30.0* C; the vapor pressure of water at this temperature is 31.8 torr. Assume that glycerin dissolves molecularly (does not dissociate).
Please answer!!
No links.
Picture is included!
Answer:
c
Explanation:
which change of phase is exothermic
Which type of monomer combines and forms polypeptides?
A. Nucleic acid
B. Amino acid
C. Fatty acid
D. Monosaccharide
one of the biggest dangers of storms that produce heavy rains or storm surges is ___.
A. Low Temperatures
B. Flooding
Answer:
B. Flooding
Explanation:
Flooding can be caused by heavy rains/storm surges. Hope this helped!
3 useful applications of alkaline earth metals
Answer:
1 used in paint , toothpaste
2 used in fireworks and magnets
3 used to manufacture alloys
1. List the ketose carbon(s) that is(are) reduced with NaBH4.
Answer:
ehh im nit sure but here!
Explanation:
LAST ATTEMPT! Covalent compound naming !
Answer:sad
Explanation:
haaaaan not
What is the interaction between geosphere and biosphere
Answer:
The Geosphere interacts with the Biosphere in various ways. For example; Geosphere creates, destroys and keeps various biosphere habitats safe. The Geosphere interacts with the Cryosphere in various ways. For example; Cryosphere receives snow from hydrosphere, glacier of Cryosphere gouges geosphere.
Explanation:
The Geosphere interacts with the Biosphere in various ways. For example; Geosphere creates, destroys and keeps various biosphere habitats safe. The Geosphere interacts with the Cryosphere in various ways. For example; Cryosphere receives snow from hydrosphere, glacier of Cryosphere gouges geosphere.
If the concentration of KMnO4 was 0.0235 M, calculate the number of moles of MnO4- ions that completely reacted with the H2C2O4
The number of moles of KMnO4 is 0.0006 moles.
The equation of the reaction is;
6 H^+(аq) + 2 МnO4^- (аq) + 5 Н2С2O4(аq) → 10 CO2 (g) + 8 H20 (l) + 2 Mn²+ (aq)
We can see that the volume of the titrant used = Final - initial burette reading
= 29.6 mL - 3.4 mL = 26.2 mL
Number of moles of H2C2O4 = 0.139 g/90 g/mol = 0.0015 moles
If 2 moles of MnO4- reacts with 5 moles of H2C2O4
x moles of MnO4- reacts with 0.0015 moles of H2C2O4
x = 2 moles × 0.0015 moles / 5 moles
x = 0.0006 moles
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50 PTS!!!! No links pls!
What is a title name for Aerobic cellular respiration?
Answer:
Like another name?
Aerobic cellular respiration is also called aerobic metabolism, cell respiration, and oxidative metabolism.
Explanation:
What is a system?
A. A piece of scientific equipment
B. A liquid in which reactions take place
C. A technique for recording data
D. An isolated piece of the world
Answer:
C
Explanation:
A system is often defined as a procedure (a way to outline steps). C makes the most sense here.
help please I'll mark you as a brainliest promise.
Answer:
Law of the Sea Treaty
LOST Local Option Sales Tax (special purpose tax)
LOST Linux One Stanza Tips
LOST Liberty Owners Special Team
LOST Looking Over Strange Terrain :-)
LOST Line Of Sight Tasking
Explanation:is this what you meant?
NEED HELP ASAP WILL GIVE BRAINLIEST
Answer:
2.83
Explanation:
Molar concentration (mol/litre) = mass/molar mass × 1000/volume(in ml)
0.849 = mass/60.09 × 1000/55.5
mass = (0.849 × 60.09 × 55.5)/1000
= 2.8314
To 2 decimal places = 2.83
What is the atomic number of an oxygen atom that has 8 protons in its nucleus? 4 6 8 12
Answer:
8
Explanation:
f an oxygen atom has 8 protons and 8 neutrons in the nucleus, what is the atomic number? 8
For an imaginary closed economy, T = $5,000; S = $11,000; C = $48,000; and the government is running a budget surplus of $1,000. Then
Based on the information given, the private savings will be $10000 and the gross domestic product is $63000.
From the information given, he following can be gotten:
T = $5,000S = $11,000C = $48,000Budget surplus = $1000Since, S = Y - C - G
11000 = Y - 48000 - G
Y - G = 48000 + 11000
Y - G = 59000
Budget surplus = T - G = 1000
5000 - G = 1000
G = 5000 - 1000 = 4000
The GDP will be:
Y - G = 59000
Y - 4000 = 59000
Y = 59000 + 4000 = 63000
Private savings = Y - T - C
Private savings = 63000 - 5000 - 48000
Private savings = 10000
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The metal which burns with a white dazzling flame is:
a) silver
b) magnesium
c) gold
d) aluminum
Answer:
MagnesiumMagnesium burns with a dazzling white flame to form magnesium oxide a powdery mass.
Explanation:
Hope this helps you !!Answer:
b) Magnesium
Explanation:
According to G double O gle, it doesn't react with cold water but reacts to hot water/steam to form magnesium. Hydroxide and Hydrogen gas is released into the air!
What do these white-precipitate reactions have in common? (choose the best
answer)
They all have a chromate (Cro, 2) ion.
They all have a chloride ( Cl-1) ion.
They all made the same color.
They all have a barium (Bat
+2) cation
Answer:
They all have a choloride(CI-1) ion
Explanation:
A Carnot engine takes 2000 j of heat from a reservoir at 500 k, does some work and discards some heat to a reservoir at 350k . how much work does it do, how much heat is discarded, and what is it's efficiency?
Answer:
Explanation:
The Carnot engine is a theoretical or conceptual heat engine that has a higher efficiency than any practical or theoretical heat engine working between the same temperature range. The theoretical efficiency of a Carnot engine is considered as the highest efficiency and no practical heat engines can operate at that efficiency. A Carnot engine draws heat energy, performs useful work and the leftover energy is released from the working substance. According to the second law of thermodynamics, there must be a temperature gradient between the heat energy drawing point and release point of the heat engine.
_________.__________ and___________ are energy science
Answer:
Chemical, Mechanical, and Nuclear Energy
Explanation:
A team of scientists is working to find the boiling point of a liquid at very low pressure. After three trials, the team has an average
of 12.3°C. An additional trial gives a result of 13.1°C. Which statement is a reasonable conclusion that can be drawn from this
result? (1 point)
O The original average should be thrown out because it could not be confirmed by new results.
O More data should be collected because the first three trials appear to be wrong.
O The original average should be used because it came from three results, not just one.
O More data should be collected to get a more reliable average.
Since it is conventional in science to use an average not just a single result, the original average should be used because it came from three results, not just one.
The boiling point refers to the temperature when the pressure of the fluid equals the atmospheric pressure. Hence, boiling occurs at atmospheric pressure.
In scientific experiments, it is common to conduct experiments more than once and obtain an average value for the measurement. In this case, the original average should be used because it came from three results, not just one.
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how many seconds are there in 15 hours show work
Answer:
54,000 seconds
Explanation:
seconds in 1 hr = 3600
secs in 15 hrs = 3600×15
→ 54000
Which law states that energy cannot be created or destroyed, but can change from one form to another?
- the law of conservation of energy
- the law of conservation of matter
- the law of gravity
- the law of motion
answer - (the law of conservation of energy)
Answer:
the law of conservation of energy
