Answer:
2.41x10²¹ atoms
Explanation:
First we calculate the mass of nickel in the coin, using the given mass and percent composition:
0.942 g * 25/100 = 0.2355 g NiThen we convert 0.2355 grams of nickel to moles, using its molar mass:
0.2355 g Ni ÷ 58.69 g/mol = 0.004 molFinally we convert moles into number of atoms, using Avogadro's number:
0.004 mol * 6.023x10²³ atoms/mol = 2.41x10²¹ atoms29. Which is the electron configuration of an atom
in the excited state?
(1) 1s 2s²2p2
(2) 1s 2s22p'
(3) 1s 2s22p5352
(4) 1s²2s²2p%35'
A student prepared a stock solution by dissolving 20.0 g of NaOH in enough water to make 150. mL of solution. She then took 15.0 mL of the stock solution and diluted it with enough water to make 65.0 mL of a final solution. What is the concentration of NaOH for the final solution
Answer:
[tex]0.769\ \text{M}[/tex]
Explanation:
Mass of stock solution = 20 g
Molar mass of NaOH = 40 g/mol
Volume of stock solution = 0.150 mL
[tex]M_2[/tex] = Concentration of NaOH for the final solution
[tex]V_1[/tex] = Amount of stock solution taken = 15 mL
[tex]V_2[/tex] = Total volume of solution = 65 mL
Molarity is given by
[tex]M_1=\dfrac{\text{Mass}}{\text{Molar mass}\times \text{Volume}}\\\Rightarrow M_1=\dfrac{20}{40\times 0.15}\\\Rightarrow M_1=\dfrac{10}{3}[/tex]
We have the relation
[tex]M_1V_1=M_2V_2\\\Rightarrow M_2=\dfrac{M_1V_1}{V_2}\\\Rightarrow M_2=\dfrac{\dfrac{10}{3}\times 15}{65}\\\Rightarrow M_2=0.769\ \text{M}[/tex]
The concentration of NaOH for the final solution is [tex]0.769\ \text{M}[/tex].
.....plllzzz heeelp me fast??
Answer:
Explanation:
It is 11
You have to prepare a pH 5.00 buffer, and you have the following 0.10 M solutions available: HCOOH (pka=3.74), HCOONa, CH3COOH (pka=4.74), CH3COONa, HCN (pka=9.31), and NaCN. Which solutions would you use?
Answer:
CH3COOH - CH3COONa since its pKa is closest to the required pH.
Explanation:
Hello there!
In this case, in agreement with the theory of buffers as solutions able to withstand severe pH changes due to the addition of acidic or basic substances, it is possible to set up a generation equilibrium expression for the acids herein given:
[tex]Ka=\frac{[A^-][H_3O^+]}{[HA]}[/tex]
Which leads to the Henderson-Hasselbach equation:
[tex]pH=pKa+log(\frac{[A^-]}{[HA]} )[/tex]
Thus, since all the buffers have [A-]=[HA]=0.10M, the log part becomes 0 and therefore the best buffer will have the closest pKa to the required pH, which is CH3COOH - CH3COONa since its pKa is 4.74.
Best regards!
[tex]CH_3COOH\; and\; CH_3COONa[/tex] can be used to prepare a pH buffer, if 0.10 M solution available of the solutions.
What is buffer?Buffer is a solution, that resist change in pH, by adding or removing H+ ions to the solution.
Maintaining a constant pH is necessary to complete many reactions.
In blood, bicarbonates maintain the pH of the body.
[tex]CH_3COOH\; and\; CH_3COONa[/tex] have approx the nearest pH, so they can be used to make a buffer.
Thus, the correct options are [tex]CH_3COOH\; and\; CH_3COONa[/tex]
Learn more about buffer
https://brainly.com/question/24188850
A reaction has a theoretical yield of 27.6 g. When the reaction is carried out, 13.4 g of the product is obtained. What is the percent yield?
A) 48.6 %
B) 206 %
C) 370 %
D) 64.7 %
Answer:
yee I'm excellent in maths and science
Chlorofluorocarbons may be harming the ozone layer by ____.
a.
adding more ozone molecules
c.
destroying ozone molecules
b.
blocking ultraviolet radiation
d.
adding carbon dioxide molecules
Please select the best answer from the choices provided
Answer:
The awnser is C. Hope that helps!!!
For each of the environments below: (1) identify your system and surroundings and (2) predict whether it would be endothermic or exothermic.a.Wood burningSystem:Surroundings:Enthalpy Change:b.Water freezingSystem:Surroundings:Enthalpy Change:c.Sweat evaporatingSystem:Surroundings:Enthalpy Change:d.Chemical hand-warmerSystem:Surroundings:Enthalpy Change:
Answer:
A) Wood burning
system : Wood.
surroundings : atmosphere
Enthalpy : Exothermic
B) Water Freezing system
System : Refrigerator
surroundings : water in the refrigerator
enthalpy change : Endothermic
C) Sweat evaporating
System : Human being
surroundings : Air nearby
Enthalpy change : exothermic
D) Chemical Hand-warmer
system : Hand warmer pack
Surroundings : human palms
Enthalpy Change : Exothermic
Explanation:
A) Wood burning
system : Wood
surroundings : atmosphere
Enthalpy : Exothermic
This system give away energy to its surroundings hence its enthalpy change is exothermic
B) Water Freezing system
System : Refrigerator
surroundings : water in the refrigerator
enthalpy change : Endothermic
The system absorbs heat from what is put inside(surroundings ) of it hence this is na endothermic system
C) Sweat evaporating
System : Human being
surroundings : Air nearby
Enthalpy change : exothermic
This is an exothermic reaction ( enthalpy change ) because the system gives out heat to the surrounding
D) Chemical Hand-warmer
system : Hand warmer pack
Surroundings : human palms
Enthalpy Change : Exothermic
There is movement of heat from the system to the surrounding hence it is an exothermic reaction
.) Neon and HF have approximately the same molecular masses. a.)Explain why the boiling points of Neon and HF differ b.)Compare the change in the boiling points of Ne, Ar, Kr, and Xe with the change of the boiling points of HF, HCl, HBr, and HI, and explain the difference between the changes with the increasing atomic or molecular mass.
Answer:
See explanation
Explanation:
a) The magnitude of intermolecular forces in compounds affects the boiling points of the compound. Neon has London dispersion forces as the only intermolecular forces operating in the substance while HF has dipole dipole interaction and strong hydrogen bonds operating in the molecule hence HF exhibits a much higher boiling point than Ne though they have similar molecular masses.
b) The boiling points of the halogen halides are much higher than that of the noble gases because the halogen halides have much higher molecular masses and stronger intermolecular forces between molecules compared to the noble gases.
Also, the change in boiling point of the hydrogen halides is much more marked(decreases rapidly) due to decrease in the magnitude of hydrogen bonding from HF to HI. The boiling point of the noble gases increases rapidly down the group as the molecular mass of the gases increases.
Help me! Who ever gets to answer and has the best answer gets brainliest (very easy!)
Answer:
Fires --> These consume fuel and convert chemical energy stored in that fuel into thermal light and sound energy.
Decay -->The breakdown of dead plants and animals releases thermal energy.
Earth --> Thermal energy comes from deep inside and it is called geothermal energy.
Which substance is soluble in water?
2Na(s) + Cl2(g) - 2NaCl(s) + 822 kj
Answer:
Is there any other part to this question? If not I'm pretty sure the answer is 205.5 kJ
Explanation:
Answer:
822 kJ; 411 kJ/mol.
Explanation:
A chemist measures the enthalpy change during the following reaction: ()()()Use this information to complete the table below. Round each of your answers to the nearest kJ/mol. 1. ()()()Solution: given reaction is 2Na + Cl2 --> 2NaCl delta H = -822 KJ 1) 1/2Na + 1/4Cl2 --> 1/2NaCl divide the coficiant of given.
A gas goes from 1L at 273 K to 2 L when heated. What is the new temp?
Answer:
Given : Diatomic molecule at 273K
'q' absorbed = positive = +100Cal = 100 x 4.184J = 418.4J
'W' done by system = negative = -209J
By first law of thermodynamics;
ΔU = q + W = 418.4 + (-209) = 209.4J
We know for diatomic molecule Cv=25R and CvΔT=ΔU
CvΔT=209.4
25RΔT=209.4
ΔT=5R209.4×2
And, Heat exchange=Cm×ΔT
where; Cm is molar heat capacity
Cm=ΔTHeat Exchange
substituting values for Heat Exchange = 418.4 and ΔT=5R209.4×2
Cm=5R
- Rachel performed an investigation to study the thermal conductivity of four different materials. She started with four identically shaped rods—each made of a different material. Then, she placed one end of each rod into a pot of boiling water, which was at 100°C.
- After five minutes, Rachel measured the temperatures of the ends of the rods that were sticking up out of the pot to see whether they got hot. Her results are shown below.
Thermal Conductivity Investigation
Material Temperature of End of Rod After 5 Minutes
Material 1 41°C
Material 2 53°C
Material 3 98°C
Material 4 59°C
- Rachel knows that one of the materials is copper and that copper conducts thermal energy very well. Which of the materials is most likely copper?
A.
material 1
B.
material 3
C.
material 4
D.
material 2
Answer:
I will have the maths book
Answer:98
Explanation:
Calculate the pH of a 0.10 M NH4Cl solution.
Answer:
Answer: pH = 2.72
Explanation:
Calculate the pH of 0.010 M HNO2 solution. The K, for HNO2 is 4.6 x 104
how many grams of silver chloride are produced from 15.0 g of silver nitrate
Answer:
4.2 g
Explanation:
How do chemists count the number of representative particles in a substance?
Help me! Who ever gets to answer and has the best answer gets brainliest
Answer:
Decay-the breakdown of dead plants..
Earth- thermal energy comes from deep inside...
Fires- these consume feul...
Explanation:
Answer:
Fires - These consume fuel and covert chemical energy stored in that fuel into thermal, light and sound energy
Decay - The breakdown of dead plants and animals produces thermal energy
Earth - Thermal energy comes from deep inside and is called geothermal energy
Explanation:
Fires, when you burn wood, you convert chemical energy from the wood into thermal (warmth from the fire), light (glow from the fire), sound (crackling sound of wood burning)
Decay - I can't explain that one to you but there are power plants that use decomposition to produce energy
Earth - Beneath the crust there is the mantle, which consists of molten rock which produces a lot of thermal energy. This can be seen in geysers, where the molten rock heats water and hot water can burst out of the surface. Applies to hot springs too
If a compressed air cylinder for scuba diving contains 6.0 L of gas at 18°C and 200 atm pressure, what volume does the gas occupy at 1.0 atm and 25°C?
Answer:
[tex]V_2=1228.9L[/tex]
Explanation:
Hello there!
In this case, given the pressure, temperature and volume of the gas, we notice that we need the combined ideal gas as shown below:
[tex]\frac{P_2V_2}{T_2} =\frac{P_1V_1}{T_1}[/tex]
Thus, solving for the final volume, V2, we would obtain:
[tex]V_2=\frac{P_1V_1T_2}{T_1P_2}[/tex]
Now, we plug in the data and make sure the temperature must be in Kelvins to obtain:
[tex]V_2=\frac{200atm*6.0L*(25+273)K}{(18+273.15)K(1.0atm)}\\\\V_2=1228.9L[/tex]
Best regards!
Reactants for a certain reaction are combined in a solution. Which solution
would have the most successful collisions and so enable the reaction to
proceed quickly?
A. A solution at low concentration and low temperature
B. A solution at high concentration and low temperature
O C. A solution at high concentration and high temperature
D. A solution at low concentration and high temperature
The correct answer is solution B!
2. A chemical's flash point is the
The gases are contained in a reaction vessel and are in equilibrium at 298 K
X2Zi â 2XZ2(g)
a. Activation energy
b. Total mass of the system
c. Molar concentration of XZ4(g)
d. Number of molecules present
e. Equilibrium constant
1. Is decreased by the addition of a catalyst?
2. Is decreased when the volume of the reaction vessel is increased and equilibrium is reestablished at 298 K?
Answer:
1) Activation energy ( A )
2) Molar concentration of X[tex]_{2}[/tex]Z[tex]_{4}[/tex](g) ( C )
Explanation:
X[tex]_{2}[/tex]Z[tex]_{4}[/tex](g) ⇄ 2XZ
1) Activation energy Is decreased by the addition of a catalyst
while Equilibrium constant will Increase and other options will still remain unaffected
2)Molar concentration of X[tex]_{2}[/tex]Z[tex]_{4}[/tex](g) Is deceased when the volume of the reaction vessel is increased and equilibrium is reestablished at 298 K
while Number of molecules present will Increase
A student is heating a crystal of alum to
determine the hydrate formula. If she removes
it from the heat before all the water has been
removed, what will happen to the calculated
hydrate formula?
A. It will not be affected by the error.
B. The mole ratio will indicate less water than was
actually present.
C. The mole ratio Will indicate less alum than was
actually present.
What is the hydronium ion concentration of a solution whose pH is 4.12?
a. 5.1 x 10–6 M
b. 7.6 x 10–5 M
c. 6.4 x 10–5 M
d. 4.4 x 10–8 M
Which describes bonding electrons in a polar covalent bond?
electrons that are not shared equally
electrons that are shared in diatomic molecules
electrons that are shared equally
Answer:
I think the third one
Explanation:
i think
Answer:
electrons that are NOT shared equally
Explanation:
6. Menthol is a member of the terpene family of natural products. It exists in a (1R, 2S, 5R) form and a (IS, 2R, 5S) form. Are these two compounds enantiomers or diastereomers?
What is mass times acceleration equal to?
Answer:
Mass (kg) × Acceleration (m/s²) = Force (N)
What would happen to the position of the equilibrium when the following changes are made to the reaction below?
2HgO(s) ↔ Hg(l) + O2(g)
1.) The pressure on the system decreases.
Which statement defines enzymatic activity? Enzymes are required to slow down biological reactions within cells. Specific enzymes can catalyze a wide variety of chemical reactions. Enzymes regulate cellular functions through feedback mechanisms. Enzymes bind substrates so that reactive groups have many different orientations.
Answer:
Enzymes are required to slow down biological reactions within cells,
this could be not sure
Answer:
D
Explanation:
Enzymes bind substrates so that reactive groups have many different orientations.
what is one property of skim milk indicating that it is a colloidal dispersion?
Answer:
it's dairy
Explanation
In what form metals are found in nature
Answer:
Metals in nature are found in rock form, mineral forms etc..
Answer:
Metals are found in rock