How many valence electrons are in Sil4?
Answer:
12 valence electrons
Explanation:
Number of valence electrons: 2 carbons (2 x 4 valence electrons= 8e-) and 4 hydrogens (4 x 1 valence electron = 4 e-) added up gives us 12 valence electrons to work with: Counting the bonds we have made shows that we have used up 10 of the 12 valence electrons leaving us with 2 to complete the octets.
plsss i need help asap ill give brainliest!!!
The varlable that a scientist changes when conducting an experiment is called the
variable.
Omanipulated
O dependent
O responding
After a reaction went to completion, the crude reaction mixture consisted of two compounds, A and B, which were isolated by extraction. After each compound was dried, their masses were found to be, 117 mg of compound A and 89 mg of compound B. Both compounds were individually recrystallized and weighed again. After recrystallization, the mass of compound A was 91 mg and the mass of compound B was 79 mg.
Calculate the percent recovery from recrystallization for both compounds.
Answer:
Percent recovery of A = 77.78%
Percent recovery of B = 88.8 %
Explanation:
Mass of impure compound A = 117 mg
Mass of impure compound B = 89 mg
Mass of A recovered = 91 mg
Mass of B recovered = 79 mg
Percent recovery of A = 91 mg/117 mg * 100
Percent recovery of A = 77.78%
Percent recovery of B = 79 mg/89 mg * 100
Percent recovery of B = 88.8 %
Which element easily gains one electron to form a negative ion?
A.
Lithium (Li)
B.
Flourine (F)
C.
Magnesium (Mg)
D.
Nitrogen (N)
Iron metal reacts with elemental oxygen to form rust according to the unbalanced reaction, Fe(s) + O2(g) → Fe2O3(s),. What is the coefficient of the iron(III) oxide, Fe2O3(s), in the balanced reaction?
a
1
b
2
c
3
d
4
Time left for this assessment:
50:27
Answer:
c. 3
Explanation:
The unbalanced reaction expression is given as:
Fe + O₂ → Fe₂O₃
To balance the expression gives the coefficient of oxygen.
Assign the coefficients a,b, c and use a mathematical approach to solve this problem:
aFe + bO₂ → cFe₂O₃
Conserving Fe: a = 2c
O: 2b = 3c
Now let c = 1, a = 2, b = [tex]\frac{3}{2}[/tex]
Multiply through by 2,
a = 4, b = 3 and c = 2
4Fe + 3O₂ → 2Fe₂O₃
The coefficient of O₂ is 3
The mass of an unidentified rock is 15.5 grams. Students determine the volume of the rock by placing the rock in a cylinder with water. What was the density of the rock that the students should have calculated?
Hint: The graduated cylinder measures volume. Read the difference in water level.
How many grams are in 4.25x10^21 molecules of sodium oxide
Answer: 0.37g
Explanation:avogadro number = 6.02214076x10^23 atoms/molecules per mole
a mole of Na2O = 2*23 + 16 = 52 g
4.25x10^21 atoms = 52*(4.25*10^21/6.02214076*10^23) = 0.37 g
If the Titan lake froze, how would the change in kinetic energy attect the speed of the more
found in the lake?
The speed of the molecules in the lake will decrease due to decrease in the kinetic energy.
What is kinetic energy?Kinetic energy is the energy due to the motion of particles.
Kinetic energy increases with increase in temperature.
Since the temperature of the lake decreases ad it freezes, the kinetic energy decrease and the speed of the molecules in the lake will decrease.
Learn more about Kinetic energy at: https://brainly.com/question/25959744
A base produces OH-1 ions when dissolved in solution
. True
. False
Answer:
i think its true
Explanation:
Silicon has three naturally occurring isotopes with thefollowing masses and natural abundances:
Isotope Mass ({\rm amu}) Abundance (%)
{\rm Si}-28 27.9769 92.2
{\rm Si}-29 28.9765 4.67
{\rm Si}-30 29.9737 3.10
Calculate the atomic mass of silicon.
b- When solutions of silver nitrate and calcium chloride aremixed, silver chloride precipitates out of solution according tothe equation
2\; \rm AgNO_3 \it (aq) \rm \;+\;CaCl_2 \it (aq) \rm \; \rightarrow \; 2\;AgCl \it (s) \rm\; + \; Ca(NO_3)_2 \it (aq)
What mass of silver chloride can be producedfrom 1.18 L of a 0.113 \it M solution of silver nitrate?
The reaction described required3.28 L of calcium chloride. What is the concentration of thiscalcium chloride solution?
c- A volume of 50.0 mL of aqueous potassium hydroxide (\rm KOH) was titrated against a standard solution of sulfuricacid (\rm H_2SO_4). What was the molarity of the \rm KOH solution if 23.7 mL of 1.50 M\rm H_2SO_4 was needed? The equation is
\rm 2KOH(\it aq\rm )+H_2SO_4(\it aq\rm )\rightarrow\rm K_2SO_4(\it aq\rm )+2H_2O(\it l\rm )
Then, Redox titrations are used to determine the amounts ofoxidizing and reducing agents in solution. For example, a solutionof hydrogen peroxide, \rm H_2O_2, can be titrated against a solution of potassiumpermanganate, \rm KMnO_4. The following equation represents the reaction:
\matrix{{\rm 2KMnO}_4(aq)+{\rm H_2O}_2(aq)+3{\rm H_2SO}_4(aq)\rightarrow&&\hfill\cr\hfill \qquad\qquad\qquad{\rm O}_2(g)+2{\rm MnSO}_4(aq)+{\rm K_2SO}_4 (aq)+4{\rm H_2O}(l)&&\hfill}
A certain amount of hydrogen peroxide was dissolved in 100.\rm mL of water and then titrated with 1.68 M\rm KMnO_4. How much \rm H_2O_2 was dissolved if the titration required13.8 mL of the \rm KMnO_4 solution?
Answer:
See explanation
Explanation:
Relative atomic mass of silicon;
(27.9769 × 0.9218) + (28.9765 × 0.0471) + (29.9738 × 0.0312) = 28.0891
2)
2AgNO3 (aq) + CaCl2(aq) ----> 2AgCl(s) + Ca(NO3)2(aq)
number of moles of silver nitrate = 1.18 L * 0.113 M = 0.133 moles
Since 2 moles of silver nitrate yields 2 moles of silver chloride
0.133 moles of silver nitrate yields 0.133 * 2/2 = 0.133 moles of AgCl
Since 2 moles of silver nitrate reacts with 1 mole of calcium chloride
0.133 moles of silver nitrate reacts with 0.133 moles * 1/2 = 0.0665 moles of CaCl2
n =CV
C =n/V = 0.0665 moles/3.28 L = 0.02 M
3) H2SO4(aq) + 2KOH(aq) -------> K2SO4(aq) + 2H20(l)
CA = concentration of acid = 1.5 M
VA = volume of acid 23.7 ml
CB = concentration of base = ?
VB= volume of base = 50 ml
NA = number of moles of acid =1
Number of moles of base = 2
From;
CAVA/CBVB =NA/NB
CAVANB = CBVBNA
CB = CAVANB/VBNA
CB = 1.5 * 23.7 * 2/ 50 * 2
CB = 0.711 M
4) Number of moles of KMnO4 = 1.68 * 19.8/1000 = 0.033 moles
If 2 moles of KMnO4 reacts with 1 mole of H2O2
0.033 moles of KMnO4 reacts with 0.033 * 1/2 = 0.0165 moles of H2O2
molar mass of H2O2 = 34 g/mol
mass of H2O2 = 0.0165 moles of H2O2 * 34 g/mol = 0.56 g of H2O2
When 3.00 moles of hydrogen molecules and 1.50 moles of oxygen molecules react, they form 3.00 moles of water
When 3.00 moles of hydrogen molecules and 1.50 moles of oxygen molecules react, they form 3.00 moles of water
according to the reaction below.
2H2+ O2 + 2H2O
How many grams of oxygen were required?
2H, + O2 + 2H2O
How many grams of oxygen were required?
Mass of Oxygen required : 24 grams
Further explanationGiven
3 moles of H
1.5 moles of O
3 moles of H₂O
Required
Mass of O
Solution
Reaction
2H₂ + O₂ ⇒ 2H₂O
Mass of Oxygen for 1.5 moles of O :
= mol x Ar O
= 1.5 moles x 16 g/mol
= 24 grams
3. Which subatomic particles account for most of an atom's mass?
4. Which subatomic particle accounts for most of an atom's volume?
3. Proton is the subatomic particle which accounts for most of an atom's mass.
4. Electrons are the subatomic particle which accounts for most of atoms volume.
Please help!! What is this
Answer: It's a redox reaction
Explanation:
Shown below is a table with plants and animals with their adaptations.
Using the description of plants and animals in the table above, which biome would all of these organisms would be best adapted to?
Answer:
Desert
Explanation:
The adaptation shown by the given plants and animals shows that they will adapted to the desert biome.
It is so because, due to high temperature of desert some desert animals like camel have the storage of fat in humps or tails; some animals have large ears such as Jackrabbits, it helps to release body heat and adapt in high temperature; plants have thick water holding tissues to reduce water loss in heat and waxy coating that keeps the plants cooler and reduce moisture loss.
Hence, the correct answer is "Desert".
what is 0.0745 in scientific notation?
Hi! Here's the answer!
7.45E2 OR 7.45*[tex]10^{-2}[/tex]
(im pretty sure im correct, so if you'd like please give me brainly :D)
The measurements below were made on four different balances:
i. 7.5 g
ii. 7.33 g
iii. 7.5201g
iv. 7.490
A student takes a reading from a balance where the display fluctuates between 7.51 g and 7.55 g. Which of the four balances above was used?
a. iv
b. iii
c. i
d. ii
Answer:
d. ii.
Explanation:
Hello!
In this case, according to the displayed decimal placed by each balance, we can notice that:
i. Displays 1 decimal place.
ii. Displays 2 decimal places.
iii. Displays 4 decimal places.
iv. Displays 3 decimal places.
Thus, since the measured-out masses have two decimal places each, we infer that the used balance was d. ii as it displays two decimal places.
Best regards!
PLEASE HELP! DUE IN 5 MINS!!
CHEMISTRY
True or false: lone pairs of electrons around the central atom do not influence the shape
of the molecule.
Answer:
False
Explanation:
Coloumb's Law shows that opposite charges (positive and negative) attract
whereas charges that are both positive or both negative repel and a TRUE or FALSE
Answer:
True
Explanation:
It is true that coulomb's law states that opposite charges attracts and similar charges repel one another.
Charges are of two different types which are:
Positive charges
Negative charges
As a general rule, opposite charges attracts. For example, positive charges attracts negative charges at all times.
Similar charges will repel one another. For example, positive charges and positive charges repel also, negative and negative charges repel one another.
Therefore, opposite charges attracts and similar charges repel.
How much voltage is needed to get 3 amps to flow through a resistance of 6ohms
Answer:
18 Volt
Explanation:
Step 1: Given data
Intensity of the current (I): 3 AmpereResistance (R): 6 OhmRequired voltage (V): ?Step 2: Calculate the required voltage
We have a continous current flowing through a resistance. We can calculate the required voltage using Ohm's law.
I = V/R
V = I × R
V = 3 A × 6 Ω = 18 V
How many moles of carbon dioxide are produced when 23.0 g of C3H2O3 is burned during the
complete combustion of C3H2O3?
O 33.0 mol
O 0.250 mol
O 0.750 mol
O 3.00 mol
O 0.0833 mol
Moles of Carbon dioxide : 0.75
Further explanationGiven
23 g C₃H₈O₃
Required
Moles of Carbon dioxide
Solution
Reaction
2C₃H₈O₃ + 7O₂ → 6CO₂ + 8H₂O
mol C₃H₈O₃ :
= mass : MW
= 23 g : 92,09382 g/mol
= 0.24975
From the equation, mol ratio of C₃H₈O₃ : 3CO₂ = 1 : 3, so mol CO₂ :
= 3/1 x mol C₃H₈O₃
= 3/1 x 0.24975
= 0.74925≈0.750 mol
The element carbon continuously Cycles through an ecosystem. A simplified carbon cycle showing Step I, where organic molecules (carbohydrates) are created, and step II where CO2, Carbon dioxide, is produced, is depicted below.Identify the process in Step I and explain how it causes the movement of carbon.
Answer:
See the answer below
Explanation:
Organic molecules in the form of carbohydrates are created during photosynthesis or chemosynthesis and these processes cause carbon to be removed from the atmosphere or other environment into the biosphere - the living organisms of the ecosystem.
During photosynthesis, atmospheric carbon dioxide is fixed as carbohydrates into green plants in a two-stage process that requires sunlight energy and water. The entire process can be summarized as an equation below:
[tex]6CO_2 + 6H_2O + sunlight --> C_6H_1_2O_6 + 6O_2[/tex]
Instead of using water as a reactant, chemosynthetic organisms make use of high energy chemicals such as hydrogen sulfide to fix carbon dioxide in order to generate carbohydrates.
[tex]CO_2 + 4H_2S + O_2 -> CH_20 + 4S + 3H_2O[/tex]
Both processes ensure that carbon dioxide moves from the environment into living organisms.
To isolate a single variable when rearranging equations, move all other variables to the__________of the equation by using ________ on them and remembering to perform that operation _________. Make sure the rearrangement has the target variable
Answer:
Explanation:
To isolate a single variable when rearranging equations, move all other variables to the other side of the equation by using its inverse operation on them and remembering to perform that operation on itself. Make sure the rearrangement has the target variable. For example, we can grab a simple equation such as the one below and isolate x.
x - 5y + 3 = 25 ... first we subtract 3 from both sides
x - 5y = 22 ... now we add 5y to both sides which will cancel out the 5y on the left
x = 22 + 5y
And we finally have the x variable isolated.
Under what conditions would wind blow weakly or very little?
50 Points and Brainliest for right answer
Answer:
A gentle wind or when the wind blows slowly, it is called a breeze.
Explanation:
Breezes are the result of differences in air temperature. Warm air rises, leaving behind low pressure near the ground. Cold air creates high pressure and sinks to compensate; wind then blows from areas of high pressure to areas of low pressure to try to equalize pressures.
Answer:
under low pressure of air makes wind blow weakly or very little.
6. What is the lowest temperature on the Kelvin scale? What happens to matter when it
reaches this temperature?
Answer:
-273.15 degrees celsius
What is the definition of silicon minerals
There are a lot of energy sources found underground. Oil is a liquid, but what is this gas down here called? Natural gas!
We use natural gas to heat our homes and to make electricity. Because it is a gas, what is the best way to transport it?
Answer: The natural gas transmission system is primarily a giant international pipeline network, consisting of large, medium, and small-sized pipes. ... If transport by pipeline is not feasible, then natural gas is usually transported in its liquefied state, which has a temperature of -162 ° C and its density is lower than waters.
Explanation: Potential energy is stored energy and the energy of position. Chemical energy is energy stored in the bonds of atoms and molecules. Batteries, biomass, petroleum, natural gas, and coal are examples of chemical energy
Please help!! Need to know what it is!
Answer:
The correct answer will be 15
Answer:
15Explanation:
it is fifteen. 15 heheheehehehhehehehehehheheheSodium metal is placed in water to produce sodium hydroxide (NaOH)
ions and hydrogen gas (H2).
Which substance in the chemical reaction is a solid?
a Sodium
b Water
C Sodium hydroxide ions
d Hydrogen vapor
Answer:
a Sodium
Explanation:
The solid in this reaction is the sodium metal. A solid is a substance held together by attractive forces that are very strong.
Solids have a fixed shape and volume.
Metals are solidsSodium is an alkali metal belonging to the first group on the periodic table. This solid combines with the liquid water. The product is an aqueous sodium hydroxide.How can you minimize a collision summary
One of the ways to minimize a collision is to slow down: When you can't find an escape and you're definitely going to collide with something, you should slow your vehicle down as much as possible.
Hope this helps ^^
