Answer:
0.275
Explanation:
Given that:
Initial number of miles of radioactive isotope = 4.4 moles
How much if the sample remains after 4 half life's
Half-life refers to the time taken by a sample to reduce to half of it's initial value.
After the first half life :
Initial / 2 = 4.4 / 2 = 2.2 moles
Second half life :
2.2 / 2 = 1.1 moles
Third half life :
1.1 / 2 = 0.55 Moles
Fourth half life :
0.55 / 2 = 0.275 moles
Imagine that you're doing an experiment to determine how the running speed
of a hamster depends on the weight of the hamster. When plotting your data,
what variable should be on the y-axis?
A. Speed of hamster
B. Color of hamster
C. Weight of hamster
D. Type of hamster
how can chemistry help solve a crime ?
plz helppp
Chemistry is vital in forensic science (used to solve crimes). With chemistry, forensic scientists demonstrate what happened on a molecular level. Chemical analysis can reveal how long ago a person died, what weapon was used, the kind of tape or rope used to tie someone up, etc. They also analyze drugs/controlled substances taken from scenes and people to identify and sometimes quantify these materials.
What is the wavelength, in nanometers, of light with a frequency of 5.89 x 10¹⁴ s⁻¹?
Answer:
≅ 50, 909 nm
Explanation:
Wavelength, λ = [tex]\frac{speed}{freq}[/tex]
Given:
speed of light = [tex]3*10^{8} m/s[/tex]
f = 5.89 × [tex]10^{14}[/tex]
∴ λ = 3×[tex]10^{8}[/tex] / 5.89 × [tex]10^{14}[/tex]
= 0.0000509 m ≅ 50, 909 nm
Let me know if you need further assistance
For molecules with multiple ionizable groups, such as glycine, which of the following statements is true?1. At a pH near the pI, nearly all the molecules carry a net positive charge.2. At pH near the pI, nearly all the molecules carry no net charge.3. At a pH near the pI, nearly all the molecules carry a net negative charge.4. When the pH is near the pI, the solution is near its
Answer:
2. At pH near the pI, nearly all the molecules carry no net charge
Explanation:
The general equilibrium for a molecule with multiple ionizable groups could be:
H₃A⁺ ⇄ H₂A + H⁺ ⇄HA⁻ + H⁺⇄A²⁻ + H⁺
Where each equilibrium has its own pKa
The equilibriums in which H₂A are involved (The neutral molecule), are used to determine the isoelectrical point.
The isoelectrical point is defined as the value of pH in which the molecule has no net charge.
Thus, true option is:
2. At pH near the pI, nearly all the molecules carry no net charge14 oz (ounces) is the same as how many lbs (pounds)?
Answer:
0.875 Pounds
Explanation:
Formula is
Just divide the mass value by 16
calculate the potential of the electrochemical cell and determine if it is spontaneous as written at
Hello. This question is incomplete. The full question is:
Calculate the potential of the electrochemical cell and determine if it is spontaneous as written at 25 ∘C . Cu(s) || Cu2+(0.14 M) ‖‖ Fe2+(0.0040 M) || Fe(s) E∘Cu2+/Cu=0.339 VE∘Fe2+/Fe=−0.440 V Ecell= V Is the electrochemical cell spontaneous or not spontaneous as written at 25 ∘C ? not spontaneous spontaneous
Answer:
Ecell = -0.825v
Negative results indicate that the electrochemical cell is not spontaneous.
Explanation:
You will find the result by doing the following calculation:
Cu2 + = 0.14M
Fe2 + = 0.0040M
Eº Cu2 + / Cu = 0.339V
Eº Fe2 + / Fe = -0.440V
Electron change ............ n = 2
Cu // Cu2 + (0.14M) // Fe2 + (0.0040M) / Fe (s)
Cu + Fe2 + ----> Fe (s) + Cu2 + (aq)
You should now use the formula =
Eºcell = Eº anode - Eº cathode ------> Eº = Eº (Fe2 + / Fe) - Eº (Cu2 + / Cu)
Eº Cell = -0.440 - 0.339 = -0.779V
E cell = EºCell - (0.0591 / n) log (Cu2 + / Fe2 +)
E cell = -0.779 - (0.0591 / 2) log (0.14 / 0.0040)
Ecell = -0.825
The estimated costs for remodelling the interior of an apartment are: three 1-gallon cans of paint at $13.69 each, two paint brushes at $9.53 each, and $135 for a helper. The total estimated cost with the appropriate significant figures is $
Answer:
$195
Explanation:
Step 1: Given data
Cost of a 1-gallon can of paint (cC): $13.69Number of 1-gallon cans of paint (nC): 3Cost of a paint brush (cB): $9.53Number of paint brushes (nB): 2Cost of a helper (cH): $135Number of helpers (nH): 1Step 2: Calculate the total estimated cost for remodelling the interior of an apartment
We will use the following expression.
C = cC × nC + cB × nB + cH × nH
C = $13.69 × 3 + $9.53 × 2 + $135 × 1
C = $195
The change that happen the piece of paper during the burning process?
Answer: Chemical
Explanation:
When paper is burned, it creates a chemical change.
Answer:
Explanation:
Hey, there!!
The answer is chemical change.
When the paper is burned it changes into an ash. Which is a chemical change. { as it can't be reversed }.
Hope it helps...
How many L are in 0.74 CL ?
Answer:
0.0074 cL
7.4 x 10⁻³ cL
Explanation:
Step 1: Find conversion
1 liter (L) = 100 centiliters (cL)
Step 2: Set up dimensional analysis
[tex]0.74cL(\frac{1L}{100cL} )[/tex]
Step 3: Multiply and cancel out units
cL and cL cancel out.
We are left with L.
0.74/100 = 0.0074 cL or 7.4 x 10⁻³ cL
Write the volume of the liquid, in milliliters, using the proper number of significant figures.Express your answer with the appropriate units.
Answer:
19.5 mL
Explanation:
MgSO4(aq) + 2NaOH(aq) Mg(OH)2(s) + Na2SO4(aq) i. Write the complete ionic equation from the balanced equation. (3 points) Please help!
Answer:
Mg²⁺(aq) + SO₄²⁻(aq) + 2Na⁺(aq) + 2OH⁻(aq) → Mg²⁺(aq) + 2OH⁻(s) + 2Na⁺(aq) + SO₄²⁻(aq)
Explanation:
The complete ionic equation is the chemical equation where the chemical species in the aqueous phase (aq) are written as ions.
In the reaction:
MgSO₄(aq) + 2NaOH(aq) → Mg(OH)₂(s) + Na₂SO₄(aq)
MgSO₄ dissociates in Mg²⁺ and SO₄²⁻, NaOH in Na⁺ and OH⁻, Mg(OH)₂ doesn't dissociate because is as solid and NaSO₄ dissociates in Na⁺ and SO₄²⁻ ions.
That means the complete ionic equation is:
Mg²⁺(aq) + SO₄²⁻(aq) + 2Na⁺(aq) + 2OH⁻(aq) → Mg²⁺(aq) + 2OH⁻(s) + 2Na⁺(aq) + SO₄²⁻(aq)Convert 1,650,000 centimeters to kilometers.
Answer:
16.5
Explanation:
Answer:
is your answer is 16.5 km
A reagent bottle contains a stock solution of 0.90% by mass of sodium chloride, NaCl.
The density of the solution is 1.00 g cm ?. Calculate
(i) the mole fraction of NaCl
(ii) the molality of NaCl solution
(111) the volume of the stock solution required to prepare 100 mL of 0.01 M NaCl
solution.
Answer:
I. 2.79x10⁻³
II. 0.155m
III. 6.49mL of the solution you must add from the stock solution
Explanation:
A solution of 0.90% by mass NaCl means that, in 100g of solution, you have 0.90g of NaCl. In other words, there are 0.90g of NaCl + 99.1g of water.
I. Mole fraction of NaCl is the ratio between moles of NaCl and total moles of solution.
Moles NaCl:
0.90g * (1mol / 58.44g) = 0.0154 moles NaCl
Moles water:
99.1g water * (1mol / 18.01g) = 5.50 moles water.
Total moles = 5.50 +0.0154 moles = 5.518 moles
Mole fraction NaCl: 0.0154 / 5.518 moles =
2.79x10⁻³II. Molality is the ratio between moles of solute (NaCl) and kg of solvent.
There are 99.1g of water = 0.0991kg.
Molality is: 0.0154 moles / 0.0991kg
0.155mII. 100mL of a 0.01M are:
100mL = 0.100L * (0.01 mol / L) = 1x10⁻³ moles of NaCl
In 100g = 100mL (Density of 1g/mL) there are 0.0154 moles. To have 1x10⁻³ moles you need:
1x10⁻³ moles of NaCl * (100mL / 0.0154 moles) =
6.49mL of the solution you must add from the stock solutionI. Mole fraction of NaCl is 2.79x10⁻³
II. Molarity of NaCl solution is 0.155m
III. 6.49mL of the stock solution required to prepare 100 mL of 0.01 M NaCl solution.
What does % by mass mean?
A solution of 0.90% by mass NaCl means that, in 100g of solution, you have 0.90g of NaCl.
Or
There is 0.90g of NaCl + 99.1g of water.
We need to find:
I. Mole fraction of NaCl:
Mole fraction can is the ratio of moles of Solute to the total number of moles of the solutes and the solvent.
Moles of NaCl(solute) = 0.90g * (1mol / 58.44g) = 0.0154 moles NaCl
Moles of water(solvent) = 99.1g water * (1mol / 18.01g) = 5.50 moles water.
Total moles = 5.50 +0.0154 moles = 5.518 moles
Mole fraction of NaCl = [tex]\frac{0.0154}{ 5.518} =2.79 * 10^{-3}[/tex]
II. Molality is a measure of the number of moles of solute(NaCl) in a solution corresponding to 1 kg or 1000 g of solvent
Since, 99.1g of water = 0.0991kg.
Molality of NaCl = [tex]\frac{0.0154 moles}{0.0991 kg}=0.155m[/tex]
III. 100mL of a 0.01M is:
100mL = 0.100L * (0.01 mol / L) = 1x10⁻³ moles of NaCl
In 100g = 100mL (Density of 1g/mL) there are 0.0154 moles. To have 1x10⁻³ moles you need:
1x10⁻³ moles of NaCl * [tex]\frac{100 mL}{0.0154 moles}[/tex] = 6.49mL of the solution you must add from the stock solution
Learn more:
https://brainly.com/question/15063496
he solubility of oxygen gas in water at 25 °C and 1.0 atm pressure of oxygen is 0.041 g/L. The solubility of oxygen in water at 2.5 atm and 25 °C is ________ g/L.
Answer:
0.1025 g/L
Explanation:
From the question above,
The solubility of oxygen gas in water at 25°c and 1.0 atm pressure is 0.041g/L
Henry's law states at a constant temperature the solubility of a gas is proportional to the pressure
Since the temperatures are both similar (25°c) then, the solubility of oxygen in water at 2.5 atm can be calculated as follows
= 0.041/1.0 × 2.5
= 0.041×2.5
= 0.1025 g/L
Hence the solubility of oxygen in water at 2.5 atm and 25°c is 0.1025 g/L
Using standard reduction potentials from the ALEKS Data tab, calculate the standard reaction free energy for the following redox reaction. Round your answer to significant digits. N2H4 + 4OH + 2Cl2
Answer:
-973 KJ
Explanation:
The balanced reaction equation is;
N2H4(aq) + 2Cl2(g) + 4OH^-(aq)---------> 4Cl-(aq) + 4H ^+(aq) + 4OH^-(aq) + N2(g)
Reduction potential of hydrazine = -1.16 V
Reduction potential of chlorine = 1.36 V
From;
E°cell= E°cathode - E°anode
E°cell= 1.36 - (-1.16)
E°cell= 2.52 V
∆G°=- nFE°cell
n= number of moles of electrons = 4
F= Faraday's constant = 96500 C
E°cell = 2.52 V
∆G°=- (4 × 96500 × 2.52)
∆G°= -972720 J
∆G°= -972.72 KJ
What volume is show in this picture?
Answer:
millileter????
Perform the calculation, rounding your answer to the proper number of significant figures.
0.8730 divided by 9.650 =
Answer:
Hey!
0.8730 / 9.650 = 8.42445
Explanation:
8.42445 TO 2 s.f... (best option for rounding)
= 8.4
ANSWER = 8.4 (2 s.f)
HOPE THIS HELPS!!
How many significant figures are in the quantity 12.0 mL?
O A. 1
B. 2
C. 3
O D. 12
Answer:
C. 3
Explanation:
12.0 - 3 significant figures 1,2 and 0, because 0 is after decimal point.
Calculate the pH and the pOH of an aqueous solution that is 0.020 M in HCl(aq) and 0.085 M in HBr(aq) at 25 °C.
Is a Animal and Plant cell living
A statement that can be proven by observation or measurement is known as a(n):
a.
opinion
b.
value
c.
fact
d.
belief
Please select the best answer from the choices provided
A
B
C
D
The correct answer for this question is that a statement that can be proven by observation or measurement is known as a fact. The other possible answers here simply refer to idea that different individuals can place value on, but that are not necessarily known to be true.
identify balance chemical equation from the following
C+O2=CO2
H2+O2=H2O
2PbO+C=Pb+CO2
Fe2O3+2Al=Al2CO3+2Fe
Answer:
C+O2=CO2
Explanation:
no.of atoms on reactant side= no.of atoms on product side
What volume of 1.25 M sodium hydroxide (NaOH) solution can be prepared using 60.0 g of sodium hydroxide? (The mass of one mole of NaOH is 40.0 g.)
0.667 L
0.833 L
1.20 L
1.88L
Answer:
The answer is
1.20 LExplanation:
Since the concentration , mass and molar mass of NaOH has been given we use the formula
[tex]C = \frac{m}{M \times v} [/tex]To find the volume
where
C is the concentration
m is the mass
M is the molar mass
v is the volume
Making volume the subject we have
[tex]v = \frac{m}{C \times M} [/tex]From the question
C = 1.25 M
m = 60 g
M = 40.0 g/mol
Substitute the values into the above formula and solve for the volume
We have
[tex]v = \frac{60}{1.25 \times 40} \\ v = \frac{60}{50} \\ v = \frac{6}{5} [/tex]We have the final answer as
Volume = 1.20 LHope this helps you
What is the molecular formula and chemical name of the compound? Examine the image. The letters Si in the center with four lines connecting it to 4 Fs, 1 in each direction.
Answer:
molecular formula is "SiF4" and compound name is "silicon tetrafluoride"
Explanation:
nder what reaction conditions does the electrophilic chlorination of aromatic compounds usually occur
Answer:
Cl2/FeCl3
Explanation:
The electrophilic chlorination of aromatic compounds proceeds in the presence of Cl2/FeCl3.
The function of the Lewis acid FeCl3 is to 'activate' the chlorine molecule towards electrophilic substitution. This occurs by the formation of a 'chlorine cation' which attacks the aromatic ring followed by deprotonation of the aromatic ring to retain the aromaticity of the compound.
Which of the following statements is not true for an exothermic reaction?a. The temp. of the surroundings increasesb. The temp of the reaction systems increasesc. The products have a higher heat content than the reactantsd. Heat passes from the reaction system to the surroundingse. The enthalpy change for the reaction is negative
Answer:
The products have a higher heat content than the reactants
Explanation:
Recall that the change in enthalpy for a reaction is obtained from
∆Hreaction= enthalpy of products - enthalpy of reactants
For an exothermic reaction, enthalpy of reactants > enthalpy of products, hence ∆Hreaction is negative.
This implies that the heat content of reactants is greater than that of products for an exothermic reaction. Hence the option selected in the answer is false as written.
define what is halflife
Answer: the time taken for the radioactivity of a specified isotope to fall to half its original value.
Explanation:
Answer:
Half-life is the time required for a quantity to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo, or how long stable atoms survive, radioactive decay.
explain why the neutralization reaction of a strong base and weak acid gives a weakly basic solution
Answer:
when an acid react with a base, salt and water is produced. It is because the nature of salt formed determines whether the solution is neutral, acidic or basic
Hope this helps :)
Why is a 9-v transistor battery used as the source of electrical power for electrolysis rather than the power supply that plugs into the wall electrical current?
Answer:
The 9-v transistor battery is a direct current source, while the power supply from the wall socket is an alternating current source.
Explanation:
A direct current (DC) is one that flows continuously without any minimum and maximum values. This is majorly obtained from generators, batteries or cells etc.
An alternating current (AC) is a type that flows in a sinusoidal manner, having minimum and maximum value with respect to its flowing frequency. An example is the one obtained from the wall electrical source , generators etc.
An alternating current is not mainly used for electrolysis because of its nature. It would cause a switch of the electrodes in every cycle. Therefore, a direct current source is used.
The 9-v transistor battery is a direct current source, while the power supply from the wall is an alternating current source.
if a mixture of 90 g of hydrogen sulfide and 70.5 g of chromium oxide are allowed to raeact what mass of water can be formed
Answer:
24.84 g
Explanation:
The balanced reaction equation is;
Cr2O3(s) + 3H2S(g) ⟶Cr2S3(s) + 3H2O(l)
We must first determine the limiting reactant
For chromium III oxide;
Amount of chromium III oxide = mass/molar mass = 70.5g/ 151.99 g/mol = 0.46 moles
If 1 mole of chromium III oxide yields 3 moles of water
0.46 moles of chromium III oxide yields 0.46 × 3 = 1.38 moles of water
For hydrogen sulphide
Amount of hydrogen sulphide = mass/molar mass = 90g/ 34 gmol-1 = 2.64 moles
If 3 moles of H2S yields 3 moles of water
2.64 moles of H2S yields 2.64 × 3/3 = 2.64 moles of water
Hence chromium III oxide is the limiting reactant.
Mass of water produced= 1.38 moles × 18gmol-1= 24.84 g