Answer:
Near the boiling point of the solvent
Explanation:
The process of recrystallization is hinged on the fact that the amount of solute that can be dissolved by a solvent increases with temperature. The process involves creation of a solution by dissolving a solute in a solvent at or near its boiling point. At the boiling point of the solvent, the solute has a greater solubility in the solvent; not much volume of the hot solvent is required to dissolve the solute.
Before the solution is later cooled, you can now filter out insoluble impurities from the hot solvent. The quantity of the original solute drops appreciably because impurities have been removed. At this lower temperature, the solution becomes saturated and the solute can no longer be held in solution hence it forms pure crystals of solute, which can be recovered.
Recrystallization must be carried out using the proper solvent. The solute must be relatively insoluble in the solvent at room temperature but more soluble in the solvent at elevated temperature.
The osmotic pressure exerted by a solution is equal to the molarity multiplied by the absolute temperature and the gas constant . Suppose the osmotic pressure of a certain solution is measured to be at an absolute temperature of . Write an equation that will let you calculate the molarity of this solution. Your equation should contain only symbols. Be sure you define each symbol other than . Your equation: Definitions of your symbols:
Answer:
c = π / R × T
Explanation:
The osmotic pressure exerted by a solution is equal to the molarity multiplied by the absolute temperature and the gas constant R . Suppose the osmotic pressure of a certain solution is measured to be 22 atm at an absolute temperature of 353 K. Write an equation that will let you calculate the molarity c of this solution. Your equation should contain only symbols. Be sure you define each symbol other than R.
Step 1: Given data and definition of the symbols
Osmotic pressure (π): 2.2 atmMolarity of the solution (c): ?Ideal gas constant (R): 0.08206 atm.L/mol.KAbsolute temperature (T): 353 KStep 2: Write an equation that will let you calculate the molarity of this solution, in terms of symbols
The osmotic pressure is a colligative property that can be calculated using the following expression.
π = c × R × T
We can rearrange this expression to calculate the molarity of the solution.
c = π / R × T
A 25.00-mL aliquot of a nitric acid solution of unknown concentration is pipetted into a 125-mL Erlenmeyer flask and 2 drops of phenolphthalein are added. The above sodium hydroxide solution (the titrant) is used to titrate the nitric acid solution (the analyte). If 12.75 mL of the titrant is dispensed from a burette in causing a color change of the phenolphthalein, what is the molar concentration of the nitric acid solution? (Show all steps for calculating the answer.)
Answer: 0.0611 M HNO3
Answer:
0.0611M of HNO3
Explanation:
The concentration of the NaOH solution must be 0.1198M
The reaction of NaOH with HNO3 is:
NaOH + HNO3 → NaNO3 + H2O
1 mole of NaOH reacts per mole of HNO3.
That means the moles of NaOH used in the titration are equal to moles of HNO3.
Moles HNO3:
12.75mL = 0.01275L * (0.1198mol / L) = 0.0015274 moles NaOH = Moles HNO3.
In 25.00mL = 0.025L -The volume of the aliquot-:
0.00153 moles HNO3 / 0.025L =
0.0611M of HNO3help pls
Which process of sedimentary rock formation occurs last?
cementation
compaction
deposition
erosion
Answer:
Compaction.
Explanation:
All the others are before this.
Which particle is negatively charged?
A. proton
B. atom
C. neutron
D. electron
Answer:
D. electron
Explanation:
Electrons have a negative charge
36.8 g of CuSO4(s) was added to water to prepare a 2.00 L solution. What is the
concentration of CuSO4 in molarity?Molar mass of CuSO4 = 159.62 g/mol
A. 18.4 M
B. 1.84 M
C. 0.231 M
D. 0.115
Answer:
Option D. 0.115 M
Explanation:
The following data were obtained from the question:
Mass of CuSO4 = 36.8 g
Volume of solution = 2 L
Molar mass of CuSO4 = 159.62 g/mol
Molarity of CuSO4 =..?
Next, we shall determine the number of mole in 36.8 g of CuSO4.
This can be obtained as shown below:
Mass of CuSO4 = 36.8 g
Molar mass of CuSO4 = 159.62 g/mol
Mole of CuSO4 =.?
Mole = mass /Molar mass
Mole of CuSO4 = 36.8 / 159.62
Mole of CuSO4 = 0.23 mole
Finally, we shall determine the molarity of the CuSO4 solution as illustrated below:
Mole of CuSO4 = 0.23 mole
Volume of solution = 2 L
Molarity of CuSO4 =..?
Molarity = mole /Volume
Molarity of CuSO4 = 0.23 / 2
Molarity of CuSO4 = 0.115 M
Therefore, the molarity of the CuSO4 solution is 0.115 M.
Rahul and Manav each were given a mixture of iron filings and sulphur powder. Rahul heated the mixture strongly and a new substance was formed. Write three points of difference between the two.Required to answer.
Answer:
sure
Explanation:
The substance formed after heating the mixture of that of Rahul is caleed a compound. Whereas, Manav's mixture still remains in its current stae that is a heterogeneous mixture.
The compound formed is in black in color whereas the mixture is a mix of brownish-red and yellow.
The compound is a homogeneous mixture whereas the mixture is a heterogenous mixture because of its uneven distribution.
There are exaclty 640 acres in one square mile. How many square meters are in 2.2 acres?
Answer:
8,903.09 square meters
Explanation:
Doing a quick search online we can see that there are exactly 4046.86 square meters in a single acre (1 acre). Therefore, we can simply use the rule of three to calculate the total amount of square meters in 2.2 acres. We do this by multiplying 2.2 acres by 4046.86 square meters and then dividing by 1 acre to solve for x.
1 acre <=====> 4046.86 square meters
2.2 acres <====> x
(2.2 * 4046.86) / 1 = x
8903.09 / 1 = x
8,903.09 = x
Finally, we can see that there are 8,903.09 square meters in 2.2 acres.
Which of the following is a common sign that a chemical change has occurred?
Answer:
C a chemical has become a different color
Explanation:
is it a chemical change when water turns to ice? or to water vapor? no because it can easily change back.
it's not A obviously
I just explained why it's not B
and again it's obviously not D
It's C because once you change the color of something you can most likely not change it back (cake batter, stained glass) making it a chemical change
The number that represents a neutral pH is . (2 points)
Answer:
7
Explanation:
Answer:
7 is your answer
YW! :)
Explanation:
Find the density of a liquid that has a mass of 24 grams and a volume of 6 ml.
Answer:
4
Explanation:
24/6 is 4.
Answer:
Mathematically: D = m/v. If you know what liquid you have, you can look up its density in a table. Once you know that, all you have to do to find the mass of the liquid is to measure its volume. Once you know density and volume, calculate mass using this relationship: mass = density • volume.
Explanation:
How did changing from a light drizzle to a downpour affect the river and the sediment un it
Answer:
The velocity of the river increased.
There was more erosion in the stream.
The type of sediment that moved changed.
Explanation:
Answer:
The river increased its slope.
The volume of the river decreased.
The velocity of the river increased.
There was more erosion in the stream.
The type of sediment that moved change
Explanation:
describe the structure and function of gamma rays
Answer:
A gamma ray is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and gives off the highest photon energy. The energy spectrum of gamma rays can be used to identify the decaying radionuclides using gamma spectroscopy.
Explanation:
Explain what happened to the electrons in the elements when you exposed them to the flame. *please help
Explanation:
When you heat an atom, some of its electrons are "excited* to higher energy levels. When an electron drops from one level to a lower energy level, it emits a quantum of energy. ... The different mix of energy differences for each atom produces different colours. Each metal gives a characteristic flame emission spectrum.
The amount of UVA radiation hitting a surface at sea level in a lightly clouded day is about 70W/m2. About half of that can be absorbed by the skin. A typical carbon- carbon bond requires 348 kJ/mol to break. A person lies on the beach for about 1 hour without sunscreen (i.e. fully exposed to UVA radiation). Estimate the number of C-C bonds broken in this person’s back (about 0.18 m2) over that period. Assume that the average wavelength of UVA is 335 nm.
Answer:
Explanation:
Area of person's back = .18 m²
energy of radiation falling on the back per second
= 70 x .18 J
= 12.6J
Energy absorbed per second = .5 x 12.6 = 6.3 J
energy absorbed per hour = 6.3 x 60 x 60 = 22680 J
energy required to break one mole bond = 348 x 10³ J
energy required to break one bond = 348 x 10³ / 6.02 x 10²³
= 57.8 x 10⁻²⁰ J .
So number of bonds broken in one hour = 22680 / 57.8 x 10⁻²⁰
= .392 x 10²³ bonds .
= 39.2 x 10²⁰ bonds .
) What would be the effect on the molarity of the NaOH solution if some of the water evaporated from the Florence flask after the NaOH solution was standardized with the KHP
Answer:
The effect is the increasing of the molar concentration.
Explanation:
When you standarize a solution of NaOH with KHP you are establish its molar concentration (That is the amount of moles of NaOH per liter of solution).
If you evaporated some water of the solution, you are increasing its concentration because volume is decreasing doing the amount of moles per liter increasing.
15
Density of Metals at Room Temperature
Density
Name of Metal
(g/mL)
Nickel
8.90
Copper
8.96
Palladium
12.02
smi Wetes
Silver
10.5
Platinum
21.4
Gold
19.32
Refer to the Density of Metals at Room Temperature table above. How is the density of a
metal related to its location on the Periodic Table?
A
As the metal's atomic number increases, the density increases.
B
As the metal's atomic mass increases, the density increases.
С
As the metal's number of valence electrons increases, the density increases.
D
As the metal's number of electron energy levels increases, the density increases.
Answer:
platinum = 21.4 I think it's letter D to be related to it.
Consider the reaction pathway graph below.
Which statement best describes this graph?
This is an exothermic reaction with a positive ΔHrxn.
This is an exothermic reaction with a negative ΔHrxn.
This is an endothermic reaction with a positive ΔHrxn.
This is an endothermic reaction with a negative ΔHrxn.
Answer:
This is an endothermic reaction with a positive ΔHrxn.
Explanation:
From the question given above, we can see clearly that the energy of the product (Hp) is greater than the energy of the reactant (Hr). This simply means that the reaction is endothermic as the enthalpy change (ΔH) for the reaction will be positive.
Enthalpy change (ΔH) = Heat of product (Hp) – Heat of reactant (Hr)
ΔH = Hp – Hr = positive
NOTE: A reaction with positive enthalphy change (ΔH) is termed endothermic reaction.
Answer:
C
Explanation:
edg 2020
If a central atom of a molecule only has two electron domains, what is the bond angle associated with the molecule?
120o
180o
90o
109.5o
Answer:
I think it's C.90º
Explanation:
Answer:
180o
Explanation:
It is 180 degrees because the central atom is the atom in the middle of two electrons. Think about it like a straight line, a straight line is equal to 180 degrees. One electron connected to the central atom will be 90 degrees and if there's another electron, it will be 180 degrees.
Hope this helps:)
A buffer contains significant amounts of ammonia and ammonium chloride.
Required:
a. Write an equation showing how this buffer neutralizes added aqueous acid (HCl).
b. Write an equation showing how this buffer neutralizes added aqueous acid (KOH).
A buffer system has been the salt solution that has been able to avoid the change in the pH with the addition of acid or base to the solution.
What is the effect of acid and base on buffer?The acid has been comprised of the hydrogen ion, and react with the base with the formation of salt, thereby limit the change in pH.
The addition of acid to the buffer solution has been given as:
[tex]\rm HCl+NH_3\;\leftrightharpoons\;NH_4Cl[/tex]
The base addition to the buffer reacts with the acid part of the buffer and forms salts to resist the change in pH.
The addition of the base, KOH to the buffer solution has been given as:
[tex]\rm KOH+NH_4^+\;\leftrightharpoons\;K^+\;+\;NH_3\;+\;H_2O[/tex]
Learn more about buffers, here:
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Which question must be answered to complete the table below?
A 3-column table with 3 rows. Column 1 is labeled alpha decay with entries alpha particles, plus 2 and low. Column 2 is labeled Beta Decay with entries no entry, electron negative 1 positron positive 1, and medium. Column 3 is labeled Gamma decay with entries gamma rays, 0 and high.
a. What kind of shielding will block beta decay?
b. What is the penetrating power of beta decay?
c. What kind of particles are produced by beta decay?
d. How massive are the particles in beta decay?
Answer:
c
Explanation:
If 25.98 mL of 0.1180 M KOH reacts with 52.50 mL of CH3COOH solution, what is the molarity of the acid solution?
Answer:
Explanation:
We shall use the formula S₁V₁ = S₂V₂
S₁ = .1180 M , V₁ = 25.98 mL
S₂ = ? , V₂ = 52.50 mL
.1180 M x 25.98 = 52.50 x S₂
S₂ = .0584 M
Molarity of the acid solution = .0584 M .
The concentration of the acid solution is 0.058 M.
The equation of the reaction is;
CH3COOH(aq) + KOH(aq) -----> CH3COOK(aq) + H2O(l)
The following are known;
Concentration of base CB = 0.1180 M
Volume of base VB = 25.98 mL
Concentration of acid CA = ?
Volume of acid VA = 52.50 mL
Number of moles of acid NA = 1
Number of moles of base NB = 1
Using;
CAVA/CBVB =NA/NB
CAVANB = CBVBNA
CA= CBVBNA/VANB
CA = 0.1180 M × 25.98 mL × 1/52.50 mL × 1
CA = 0.058 M
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In carbon dioxide (CO2), there are two oxygen atoms for each carbon atom. Each oxygen atom forms a double bond with carbon, so the molecule is formed by two double bonds.
Two double bonds means that the total number of electrons being shared in the molecule is
Answer:
The Answer is eight.
Explanation:
Sorry if it's too late and it doesn't help! But I hope you have a magnificent day! :3
Answer:
8
Explanation:
I had this question on my quiz and got it right.
A 500. mL gas sample is collected over water at a pressure of 740 mmHg and 25.0 °C. What is the volume of the dry gas at STP?
Answer:
Volume of dry gas at STP = 0.432 liters or 432 ml
Explanation:
Given:
Pressure (P) = 740 mmHg - 24 mmHg = 716 mmHg
Temperature (t) = 25 degrees C + 273 K = 298 K
500 ml = 0.5 l
Find:
Volume of dry gas at STP
Computation:
[P1][V1] / T1 = [P2][V2] / T2
[716][0.5] / 298 K = [760][ x Liters] / 273 K
x = 0.432 Liters
Volume of dry gas at STP = 0.432 liters or 432 ml
According to the following reaction, how many grams of hydrofluoric acid will be formed upon the complete reaction of 25.6 grams of water with excess silicon tetrafluoride?
silicon tetrafluoride (s) + water (l) → hydrofluoric acid (aq) + silicon dioxide (s)
Answer:
56.89 g of HF
Explanation:
We'll begin by writing the balance equation for the reaction. This is illustrated below:
SiF₄ + 2H₂O —> 4HF + SiO₂
Next, we shall determine the mass of H₂O that reacted and the mass of HF produced from the balanced equation.
This is illustrated:
Molar mass of H₂O = (2×1) + 16 = 2 + 16 = 18 g/mol
Mass of H₂O from the balanced equation = 2 × 18 = 36 g
Molar mass of HF = 1 + 19 = 20 g/mol
Mass of HF from the balanced equation = 4 × 20 = 80 g
Summary:
From the balanced equation above,
36 g of H₂O reacted to produce 80 g of HF.
Finally, we shall determine the mass of HF produced from the reaction. This is illustrated below:
From the balanced equation above,
36 g of H₂O reacted to produce 80 g of HF.
Therefore, 25.6 g of H₂O will react to produce = (25.6 × 80)/36 = 56.89 g of HF.
Thus, 56.89 g of HF were produced from the reaction.
A solution of 400mg of optically active 2-butanol in 10 mL of water, placed in a 20 cm cell shows an optical rotation of 40o. What is the specific rotation of this compound?
Answer:
Specififc rotation [∝] = 0.5° mL/g.dm
Explanation:
Given that:
mass = 400 mg
volume = 10 mL
For a solution,
The Concentration = mass/volume
Concentration = 400/10
Concentration = 40 g/mL
The path length l = 20 cm = 2 dm
Observed rotation [∝] = + 40°
Specififc rotation [∝] = ∝/l × c
where;
l = path length
c = concentration
Specififc rotation [∝] = (40 / 2 × 40)
Specififc rotation [∝] = 0.5° mL/g.dm
Using the specific rotation formular, the specific rotation obtained for the compound ls 5°
Given the Parameters :
Observed rotation, [tex] \alpha = 40° [/tex] Path length, l = 20 cm = 2 dmConcentration, C
Concentration = mass × volume
Mass = 400 mg = 400 /1000 = 0.4g
Volume = 10 mL
Concentration = 0.4g × 10 mL = 4g/mL
The specific rotation formular, [tex] [\alpha] [/tex] is given by :
[tex] [\alpha] = \frac{\alpha_{observed}}{C \times l} [/tex]
[tex] [\alpha] = \frac{40°}{4 \times 2} = \frac{40°}{8} = 5° [/tex]
Therefore, the specific rotation of the compound ls 5°
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Question 14 (1 point)
Calculate the molarity of a solution made by dissolving 15.25 g lithium chloride (Lici)
in 250 mL of solution
61 M LICI
2
1.4 M LICI
5
0.36 M LICI
18
0.061 M Lici
0.0014 M LICI
Answer:
Molarity = 1.4 M
Explanation:
Given data:
Mass of LiCl = 15.25 g
Volume of solution = 250 mL (250/1000 = 0.25 L)
Molarity of solution = ?
Solution:
Molarity is used to describe the concentration of solution. It tells how many moles are dissolve in per litter of solution.
Formula:
Molarity = number of moles of solute / L of solution
Now we will calculate the number of moles of LiCl.
Number of moles = mass/molar mass
Number of moles = 15.25 g/ 42.39 g/mol
Number of moles = 0.36 mol
Molarity:
Molarity = 0.36 mol / 0.25 L
Molarity = 1.4 M (M= mol/L)
A plant uses carbon dioxide and water to form food and oxygen. Why is this a chemical change?
Answer:
The plant uses carbon dioxide and water to make an entirely new chemical hence chemical change.
Explanation:
Plants create their own 'food', they turn carbon dioxide water and sunlight to create starch and glucose..
Answer:
The properties of carbon dioxide and oxygen are different.
Explanation:
im taking the exam right now and Im pretty sure it's D The properties of carbon dioxide and oxygen are different.
How does an anion form?
A. An anion forms when a stable atom loses one or more neutrons.
B. An anion forms when a stable atom loses one or more protons.
C. An anion forms when a stable atom gains one or more electrons.
D. An anion forms when a stable atom loses one or more electrons.
Fossils in the gobi desert helped scientists learn?
Answer:
dinosaurs laid eggs,sabretooths were carnivores, bats lived millions of years ago ,fossils of cynobacteria exist?
Explanation:
Question 1 of 10
What is technology?
A. An understanding of something new.
B. The steps that engineers go through to create a product.
C. Something created using science for use by society.
D. A method that is used to solve problems,
SUBMIT
Answer:
C.
Explanation:
You can use the series of elimination for this. First, you look at A. Technology is not an understanding of something new, so we cross that out. Second, you look at B. Technology isn't a series of steps, so we can mark that one off. Third, you look at C. Technology is something created using science for use by society, so we can keep that in mind. Lastly, we check D. Technology doesn't match up to the definition, so we can cross that one out. The answer that would make the most sense would be D.