Answer: 23 g
Explanation:
Amountafter = Amountbefore * (1/2)^(t/thalf)
Amountafter = (750 grams) * (1/2)^(62.0 hours/12.4 hours)
Amountafter = 23.4375 grams
750 has 2 significant digits
12.4 and 62.0 have 3 significant digits
So we take the lower of 2 significant digits:
23 grams
The half-life of 42K is 12.4 hours. 23.4375 grams of a 750 grams sample left after 62.0 hours.
What is Half Life ?Half life is the amount of time required to reduce to one-half of its initial value. The symbol of half life is [tex]t_{1/2}[/tex].
How to calculate the remaining quantity when half life given ?It is expressed as:
[tex]N(t) = N_{0} (\frac{1}{2})^{\frac{t}{t_{1/2}}[/tex]
where,
N(t) = quantity remaining
N₀ = initial quantity
t = elapsed time
[tex]t_{1/2}[/tex] = half-life of the substance
Here,
N₀ = 750.0 g
t = 62 hr
[tex]t_{1/2}[/tex] = 12.4
Now put the values in above equation we get
[tex]N(t) = N_{0} (\frac{1}{2})^{\frac{t}{t_{1/2}}[/tex]
[tex]N(t) = 750 \times (\frac{1}{2} )^{\frac{62}{12.4}}[/tex]
[tex]N(t) = 750 \times (\frac{1}{2})^5[/tex]
[tex]N(t) = 750 \times \frac{1}{32}[/tex]
N(t) = 23.4375 grams
Thus, from the above conclusion we can say that the 23.4375 grams of a 750 grams sample left after 62.0 hours.
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What does it mean if an element has 8 valence electrons?
Answer:
the answer is the D, it has a full octet
current electricity occurs naturally(true or false)
Answer:
True
Explanation:
What is the number of carbon atoms in a cycloalkyne with 8 hydrogen atoms
Answer:
4
Explanation:
C4H8
What is the amount of sodium hydroxide, NaOH, in 4.6 g? Use the values given for
the atomic mass of Na, H, and O.
6
Na = 22.989 770 u
H = 1.007 94u
0 = 15.99944
9
a) 0.19 mol
12
b) 0.12 mol
15
c) 1.8 x 102 mol
d) 0.20 mol
Answer: 0.12 Mol
Explanation: Molecular mass of NaOH is = 39,997 g/mol which is Atomic mass of Na + Atomic Mass of H + Atomic mass of O
4.6g / 39.997g/mol = 0.12 mol
types of radioactive nuclide
Answer:
On Earth, naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides, and cosmogenic radionuclides. Radionuclides are produced in stellar nucleosynthesis and supernova explosions along with stable nuclides.
Is hand washing a chemicals change or physicals change and why?
Answer:
If you wash your hands with soap, the soap molecules act as a link between the water you're washing with and the oil on your skin.
Explanation:
Bacteria and mold break down fallen leaves on the forest floor. When they do
this, they release carbon dioxide into the atmosphere and ntrogen to the
soil. Which of the following roles do bacteria and mold have in the
environment?
Answer:
H
Explanation:
not sure tho sorry if I'm wrong
I need help with both of the questions fast plz!!!
Answer: SMALLEST is lithium
LARGEST is Fluorine
Explanation:
What percentage of the total atomic mass of magnesium bromide (MgBr2) is composed of bromine? Hint - consider the mass of both atoms of bromine in your calculation. A.43% B.87% C.13% D.63%
Answer:
B. 87%
Explanation:
First, we calculate the molecular mass of magnesium bromide (MgBr2) as follows;
MgBr2 = 24.3 + 79.9(2)
= 184.1g/mol
Since 1 atom of bromine contains 79.9g, then the mass of two atoms of bromine (Br2) is 79.9 × 2 = 159.8g
Hence, the percentage of bromine (Br2) in MgBr2 is calculated as follows:
% mass of Br2 = mass of Br2/ molecular mass of MgBr2 × 100
% mass of bromine = 159.8/184.1 × 100
% mass of bromine = 0.8680 × 100
% mass of bromine = 86.8%
Approximately, % mass of bromine is 87%
What is the total mass of a 10 gram sample of 42K that will
remain unchanged after 12.4 hours?
A 2.5 g
B 5.0g
C 7.5 g
D 10 g
True or False: Electrons are significantly smaller than protons and neutrons, we can ignore electrons when we consider the physical property of an atom.
Answer:
true
Explanation:
How many moles of Mercury ll oxide are needed to produce 125g of o2
Calcular el porcentaje de cada elemento en los compuestos químicos dados.
1. KNO3 (Nitrato de potasio: fertilizante): %K=? , %N=? , %O=?
Answer:
%K=38,6% %N=13,86% %O=47,54%
Explanation:
%K=M K/M KNO3
=39/101
=38,6%
%N=14/101
=13.86%
%O=100%-%K-%N
=100-38,6-13,86
=47,54%
sodium chloride (NaCl) is an ionic compound that we consume everyday as a table salt,
what is the reason that the structure of the ionic compound causes the compound to be hard
and shiny? *
Answer:
See Explanation
Explanation:
Ionic compounds are composed of crystals. The crystal structure of an ionic compound is responsible for its hardness.
A crystalline solid contains a well organized structure which enables it to be hard and have a particular geometric shape as well defined melting point.
Hence, all the observed characteristics of NaCl are the result of its crystalline structure.
Las levaduras son microorganismos usados en la industria alimentaria en diversos procesos, uno de ellos es la fermentación del azúcar para producir alcohol, tal como se representa en el esquema. LEVADURA + AZÚCAR + CALOR ⇒ Dióxido de carbono + alcohol ¿Por qué este proceso se considera una reacción química? *
Porque solamente hay un aumento de temperatura.
Porque el azúcar cambia de estado.
Porque el azúcar se transforma en otra sustancia.
Porque el alcohol se evapora rápidamente.
Respuesta:
Porque el azúcar se transforma en otra sustancia.
Explicación:
Consideremos el cambio representado en el siguiente esquema.
LEVADURA + AZÚCAR + CALOR ⇒ Dióxido de carbono + alcohol
¿Por qué este proceso se considera una reacción química?
Porque solamente hay un aumento de temperatura. NO. El aumento de temperatura no indica una reacción química. Porque el azúcar cambia de estado. NO. El azúcar no cambia de estado. Porque el azúcar se transforma en otra sustancia. SI. En una reacción química, unas sustancias (reactivos) se transforman en otras (productos). Porque el alcohol se evapora rápidamente. NO. La evaporación es un cambio físico.energy the ability to do ____ or cause ____ its measured in _____ and is found in many different _____. energy can be classified as _____ or _____ energy
PLS HELP QUICK!!!!!
An inflated balloon contains X air molecules.After some time the volume of the balloon is found to be the half at the same temperature and pressure when a few air molecules are expelled out. a)How many molecules will be there in the balloon now? b) Which is the gas law associated with this?
Answer:
See explanation
Explanation:
According to Avogadro's law, the volume of a given mass of gas is directly proportional to the number of molecules of gas present at constant temperature and pressure.
Hence; V1/n1 = V2/n2
The implication of this is, if there were X molecules present and the volume of the balloon is halved, the number of molecules of gas present is also halved. So, we now have X/2 number of gas molecules present in the balloon.
This is in accordance with the statement of Avogadro's law.
Which pure substance can be classified as an element?
Answer:
A substance that cannot be broken down into chemically simpler components is an element.
Aluminum, which is used in soda cans, is an element.
The table below gives some characteristics of element Y
what is the identity of Y
Answer:
I doint understand that question resend it again
PLEASE HELP PLS LFHLFATOI;RHG
Answer:
C. A model of a water molecule
Explanation:
H20, model shows 2 H,s (H2) and 1 O (O) which makes H2O. It's a model and not a real life picture of a molecule.
Answer:
C. A model of a water moleculeExplanation:
2 hydrogen + Oxygen= water molecule#CarryOnLearning
[tex]{.hope (it helps}}) [/tex]
Which characteristic of water allows its molecules to form hydrogen bonds? (1 point)
Answer:
Water molecule is polar.
Explanation:
The partial negative charge on the O of one molecule can form a hydrogen bond with the partial positive charge on the hydrogens of other molecules.
9. The prefix oct- means
That there are
8 hydrogen atoms
8 carbon atoms
8 single bonds
8 double bonds
Answer:
2nd option
Explanation:
it means that there are 8 carbons
The prefix oct- mean that there are 8 carbon atoms. Therefore, option (B) is correct.
What are the steps for the IUPAC nomenclature?The 1st step for the IUPAC nomenclature of a compound is to select the longest, most substituted carbon chain with a functional group. Then the use of the primary suffix indicates the degree of unsaturation such as 'ane' or 'ene.
Then the identification of the secondary suffix indicates the number of functional groups in the molecule and the number of times of the same functional group such as di, tri, tetra, etc.
The prefix can be used to indicate the side chains, substituents, and low-priority functional groups. The prefix Oct- is used if there are eight carbon atoms in the chain. The prefix 'ane' is used for single bonds and the prefix 'ene' is used for the double bonds in the carbon chain.
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Charles's law describes the relationship of the volume and temperature of
gas at a constant mass and pressure. According to this law, what would
happen to the temperature of the gas if its volume decreased from 1.0 L to
0.50 L?
O A. The temperature would decrease by 500 K.
O B. The temperature would double.
O C. The temperature would be reduced by half.
O D. The temperature would increase from 500 K to 1000 K.
Answer:
The temperature would be reduced by half
Explanation:
Charles' Law => V ∝ T => V = kT => k = V/T
For two sets of T vs V conditions, the system constant (k) remains unchanged and k₁ = k₂ => V₁/T₁ = V₂/T₂.
Therefore, if V₁ is reduced to 1/2V₁ = V₂ => V₁/T₁ = 1/2V₁/T₂ => V₁/T₁ = V₁/2T₂
and solving for T₂ => 1/T₁ = 1/2T₂ => 2T₂ = T₁ => T₂ = 1/2T₁
∴ The initial temperature (T₁) would be reduced by half or, T₂ = 1/2T₁
A stretched spring has an elastic potential energy of 35 J when it is stretched 0.54 m. What is the spring constant of the spring? Round your answer to two significant figures.
StartFraction N over m EndFraction
Answer:
240 N/m
Explanation:
Using the formula as follows:
U = ½kx²
Where;
U = elastic potential energy (J)
K = spring constant (N/m)
x = stretched displacement (m)
According to the information provided in this question,
U = 35J
x = 0.54m
k = ?
U = ½kx²
35 = ½ × k × 0.54²
35 = ½ × k × 0.2916
35 = 0.2916k/2
70 = 0.2916k
k = 70 ÷ 0.2916
k = 240.05
To 2s.f, the spring constant (k) = 240 N/m.
Answer: 240
Explanation:
All molecules have London forces between them, but dipole-dipole and hydrogen bonding are so much stronger that when they are present we
can ignore London forces. Only NONPOLAR molecules will SHOW LDF. Which of these has ONLY LDFs?
A. I2
B. HF
C. NH3
D.H2S
Answer:
a
Explanation:
khan academy
Among the options given, only [tex]I_2[/tex] shows London-Dispersion forces. Thus, the correct option for this question is A.
What is the London-Dispersion force?The London-Dispersion force may be defined as a type of provisional attractive force that arises when the electrons in two adjacent atoms tenanted positions that construct the atoms to form temporary dipoles. It is considered the weakest intermolecular force.
[tex]H_2S[/tex] shows dipole-dipole interactions because hydrogen and sulfur have huge electronegative differences. Due to this, their bonds are polar. [tex]NH_3[/tex] shows hydrogen bonding between them. HF shows dipole-dipole interactions because it is a polar covalent molecule.
Therefore, only [tex]I_2[/tex] shows London-Dispersion forces. Thus, the correct option for this question is A.
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Explain the steps needed to obtain an ammonium salt
Answer:
When an amine is added to a solution of a strong acid, such as hydrochloric acid, the amine nitrogen atom is protonated to produce an ammonium salt. Ammonium salts of low molecular weight are soluble in water if the hydrocarbon portion of the amine is small.Ammonium cation is found in a variety of salts such as ammonium carbonate, ammonium chloride and ammonium nitrate. Most simple ammonium salts are very soluble in water. An exception is ammonium hexachloroplatinate, the formation of which was once used as a test for ammonium.
summarize what you know about carbon
Answer:
Carbon is a chemical element, like hydrogen, oxygen, lead or any of the others in the periodic table. Carbon is a very abundant element. It exists in pure or nearly pure forms – such as diamonds and graphite – but can also combine with other elements to form molecules.
Identify one natural process that may cause sudden climate changes.
Answer:
Global Warming , Volcanic Eruption
What happens in nuclear fusion?
A. Isotopes are made from gamma rays.
B. Two separate nuclei form one nucleus.
C. Missing mass is added back to a nucleus.
D. Nuclei spontaneously break down.
If 81g of water is measured out, how many moles are in the sample? *
A. 4
B. 5
C. 2.5
D. 4.5
Answer:
D
Explanation:
because moles = mass /mr
so 81/18(mr of H2O=2+16)
moles =4.5
hope this helps:)