Select the correct answer.
A sample taken from a layer of mica in a canyon has 2.10 grams of potassium-40. A test reveals it to be 2.6 billion years old. How much
potassium-40 was in the sample originally if the half-life of potassium-40 is 1.3 billion years?
O A.
4.20 g
O B.
8.40 g
O C.
12.6 g
• D.
16.8 g
O E.
25.2 g
Answer:
8.36 g
Explanation:
From;
0.693/t1/2 = 2.303/t log (No/N)
t1/2 = half life of potassium-40
t = age of the sample
No= initial amount of the sample
N= amount of the sample at time t
Substituting values;
0.693/1.3 × 10^9 = 2.303/2.6 × 10^9 log (No/2.10)
5.33 × 10^-10 = 8.86 × 10^-10 log (No/2.10)
5.33 × 10^-10/8.86 × 10^-10 = log (No/2.10)
0.6 = log (No/2.10)
Antilog (0.6) = (No/2.10)
No = 2.10 × Antilog (0.6)
No= 8.36 g
is it true that the most reactive metals are quite plentiful in the Earth's crust?
Answer:
yes
Explanation:
as it had got crushed down in the dinosaurs age
5. Which choice best represents the relationship between wavelength and frequency?
when frequency decreases, wavelength decreases
there is no relationship
when frequency increases, wavelength increases
O when frequency decreases, wavelength increases
When an Li atom becomes an Li+ ion, the Li atom
Answer:When a lithium atom forms an Li+ ion, the lithium atom (1) gains a proton (2) gains an electron (3) loses a proton (4) loses an electron
Example of fundamental units?
Answer:
are the units of the fundamental quantities, as defined by the International System of Units
Explanation:
because
In what way are electrons quantized?
O A. They have fixed energy values.
they
OB. They can be gained and lost.
O C. They are negatively charged.
O D. They form bonds in molecules.
Answer: The correct option is A) They have fixed energy values.
Explanation:
Electron is one of the sub-atomic particle present around the nucleus of an atom which is negatively charged.
In an atomic model, it is assumed that the electron revolves around the nucleus in discrete orbits having fixed energy levels.
These electrons when jumping from one energy level to another, some amount of radiation is either emitted or absorbed.
These fixed energy levels are given by the Bohr model and thus, the electrons are quantized.
Hence, the correct option is A) They have fixed energy values.
Answer: They have fixed energy values
Explanation: a pex
A toy car that is 0.12 m long is used to model the actions of an actual size car that is 6 m long which ratio shows the relationship between the sizes of the model and the actual car ?
Answer:
The correct answer is - 1:50.
Explanation:
Given:
Model toy car = 0.12 m
Actual size of car = 6 m
The ratio of model and actual car size = ?
Solution:
We know that 1 m = 100 cm
then, Model toy car - 0.12*100 = 12 cm
and size of the actual car - 6*100 - 600 cm
Then the ratio of model and actual car size = model car size/ actual car size
= 12/600
= 1/50
Thus, the correct answer is - 1:50.
A student who is performing an experiment must measure out 0.02-mL of 0.50-M HCl. The most accurate piece of equipment to measure the quantity would be a?
A) 50 mL buret
B) 25 mL graduated cylinder
C) 10 mL cylinder
D) 1 mL pipet
Answer:
Choice D) 1 mL pipet
Explanation:
If you are trying to extract 0.02 mL of HCl, you are going to need a piece of equipment that can measure very small units. Thus, Choice D would be the correct answer.
Una muestra de 2,5000 (g) de piedra caliza, se disuelve y se precipita el Calcio como oxalato de Calcio (CaC2O4), este precipitado se calcina transformándose en Carbonato de Calcio (CaCO3). El peso de este compuesto es de 1,2093 (g). Calcular el % de Calcio en la muestra
Answer:
[tex]\%Ca=19.378\%[/tex]
Explanation:
¡Hola!
En este caso, basado en la información dada, es posible conocer la masa de calcio en carbonato de calcio, que de hecho es la misma en la muestra, al utilizar el siguiente esquema de cálculo:
[tex]m_{Ca}=1,2093gCaCO_3*\frac{1molCaCO_3}{100.1gCaCO_3}*\frac{1molCa}{1molCaCO_3}*\frac{40.1gCa}{1molCa}\\\\m_{Ca}=0.48444gCa[/tex]
Finalmente, calculamos el porcentaje requerido como sigue:
[tex]\% Ca=\frac{0.48444g}{2.5000g} *100\%\\\\\%Ca=19.378\%[/tex]
¡Saludos!
What BEST describes these three molecules?
A helium tank has a volume of 13.0 L at a pressure of 26.5 atm. What is
the volume of the same amount of helium at a pressure of 1.25 atm?
Answer: 275.6 L
Explanation: We use Boyle's Law to solve this.
The initial pressure (P1) is 26.5, the initial volume (P1) is 13.0 L[tex]344.5/1.25[/tex], and the final pressure (P2) is 1.25. Using Boyle's Law, we plug in the values into the equation.
P1V1=P2V2
(26.5 atm)(13.0 L) = (1.25 atm) V2
As a regular equation, we solve for V2.
344.5 atm/L= (1.25 atm) V2
344.5 atm/L / 1.25 atm = V2
275.6 = V2
The atm value cancelled out and we are just left with the L value.
You have seen that in most of the packed foodstuff,an expiry date is usually printed.If we use that food-stuff after the expiry date,it gives a bad smell and a bad taste. i) Why does the food give a bad taste and bad smell after the expiry date ii) Write any two methods used by the food industry to prolong the life of packed food.
Explanation:
For (i):The oxidation reaction is defined as the reaction where the gain of oxygen atoms or the loss of hydrogen atoms takes place.
Foodstuff tastes bad and releases A bad odour due to the oxidation of food items and this process is called rancidity.
For (ii):To prevent food from getting rancid, various processes can be used:
Using airtight containers to avoid contact with oxygenUsing anti-oxidation to avoid oxidationInserting nitrogen gas into the packaged food itemsSe trata 50 g de aluminio que posee 10% de impurezas con suficiente cantidad de ácido sulfúrico ¿qué peso de sulfato de aluminio se obtiene si el porcentaje de rendimiento fue de 70%? P.A. (uma): Al: 27, S = 32, O = 16
Respuesta:
199.5 g
Explicación:
Paso 1: Escribir la reacción balanceada
2 Al + 3 H₂SO₄ ⇒ Al₂(SO₄)₃ + 3 H₂
Paso 2: Calcular la masa pura de 50 g de Al
Aluminio tiene 10% de impurezas, es decir, 10% de 50 g = 5 g. Luego, tiene 50 g - 5 g = 45 g de Al puro.
Paso 3: Calcular la masa teórica de Al₂(SO₄)₃ obtenida a partir de 45 g de Al
La relación de masas de Al₂(SO₄)₃ a Al es 342:54.
45 g Al × 342 g Al₂(SO₄)₃/54 g Al = 285 g Al₂(SO₄)₃
Paso 4: Calcular la masa real de Al₂(SO₄)₃ obtenida
El rendimiento de la reacción es de 70%.
285 g × 70% = 199.5 g
Nitrogen in plants and soil is changed into nitrogen compounds by _____.
nitrogen fixation
respiration
denitrification
photosynthesis
Answer:
A
Explanation:
because It's the process by which atmospheric nitrogen is converted either by a natural or an industrial means to form of nitrogen such as ammonia.
6 ways of saving energy
Answer: 21 tips: no-cost ways to save electricity
Turn off unnecessary lights.
Use natural light.
Use task lighting.
Take shorter showers.
Turn water off when shaving, washing hands, brushing teeth.
Fix that leaky faucet.
Unplug unused electronics.
Ditch the desktop computer.
Explanation:
Hope it helps you if not sorry
What similarities are there between Beta Radiation and Alpha Radiation
The largest particle, Alpha, has the least penetrative power. Positive charge is carried by alpha particles. Two neutrons and two protons are bound together to form an alpha particle. The helium-4 nucleus was later identified as the alpha particle. Among the three types of radioactive emissions, alpha particles have the most mass. An alpha particle has approximately 8000 times the mass of a beta particle. The penetrative power of an alpha particle is reduced due to its large size.
Beta particles are negative-charged high-energy electrons or positrons. Beta particles have a higher penetrative power than alpha particles due to their smaller size.
Hope this helps and if it does, don't be afraid to give my answer a "Thanks" and maybe a Brainliest if it's correct?
PLEASEE HELLLPPP mE WITH THE QUESTIONS I POSTE DIL MARK U THE BRAINLIEST I SWEAAARr
Answer:
PIEASE E first write question
sains
baby 6 Said dan alkali
Answer:
your image is not proper
Antara berikut ciri manakah bear tentang cuka?
A. Berasa pahit.
B. Berasa tawar.
C. Nilai pH kurang dari 7
D. Nilai pH ialah 7
Answer:
c. nilai pH kurang dari 7
Explanation:
cuka adalah acid
nilai pH bagi acid adalah
antara 1 hingga 6
6. Which of the following could be a base in a water solution?
a. Br-
b. NH+4
c. H2O
d. NO-3
e. Ca2+
f. C2H3O-2
Answer:
h20
Explanation:
H2O is an acid and a base, and H20 is water.
In your OWN words explain how season are formed
Answer: Weather currents change wind tempature and there for change the weather of the seasons.
Determine el PH y el % de disociación de una solución de ácido débil, sabiendo que se disuelven 20 gramos del ácido (masa molar= 55 grs) en un volumen total de 2100 ml. Ka=1,65 x 10 -8
Answer:
pH = 4.27. Porcentaje de disociación: 0.03%
Explanation:
El pH de un ácido débil, HX, se obtiene haciendo uso de su equilibrio:
HX(aq) ⇄ H⁺(aq) + X⁻(aq)
Donde la constante de equilibrio, Ka, es
Ka = 1.65x10⁻⁸ = [H⁺] [X⁻] / [HX]
Como los iones H⁺ y X⁻ vienen del mismo equilibrio podemos decir:
[H⁺] = [X⁻]
[HX] es:
20g * (1mol/55g) = 0.3636moles / 2.100L = 0.1732M
Reemplazando es Ka:
1.65x10⁻⁸ = [H⁺] [H⁺] / [0.1732M]
2.858x10⁻⁹ = [H⁺]²
5.35x10⁻⁵M = [H⁺]
pH = -log[H⁺]
pH = 4.27El porcentaje de disociacion es [X⁻] / [HX] inicial * 100
Reemplazando
5.35x10⁻⁵M / 0.1732M * 100
0.03%1. The science that deals with heredity and the factors affecting the transmission of the characteristics is
2. The trait that is usually hidden and will just come out on the second generation is
3. The appearance of the offspring is referred to as
4. The genetic make-up of the genes of the offspring is
5. Having two identical alleles of a particular gene or genes is called
6. The father of Science of Genetic is
7. It is the trait that is being expressed in an organism.
8. The extent to which something is probable is
9. The offspring of two plants/animals of different species or varieties is called
10. It is the number of times that the genotype would appear in an offspring after a test cross is
11. The relative number of offspring manifesting a particular trait or a combination of traits.
12. Having two different alleles of a particular gene or genes is
Answer:
1-Genetics
2-Alleles
3-Organism's genotype
4-Phenotypes and Genotypes
5-Allele
6-Gregor Mendel
7-Genotype
8-Probability
9-Hybrid
10-Genotypic Ratio
11-Phenotypic ratio
12-Heterozygous
Explanation:
what is the purpose of environmental regulations on chemicals
Answer: EPA regulates the production and distribution of commercial and industrial chemicals, in order to ensure that chemicals for sale and use in the United States do not harm human health or the environment.
Explanation:
Which ionic equation describes a redox reaction? A. Ag(+) + Cl- = AgCl B. 2H(+) + CO3(2-) = CO2 + H2O C. H(+) + OH(-) = H2O D. Zn + Cu(2+) = Zn(2+) + Cu The marking scheme of the past paper this question is from says that the answer is D but how?
Answer: The correct option is D. [tex]Zn+Cu^{2+}\rightarrow Zn^{2+}+Cu[/tex]
Explanation:
Redox reaction is defined as the reaction in which oxidation and reduction take place simultaneously. It is known as the reaction in which the exchange of electrons takes place.
The oxidation reaction is defined as the reaction in which a chemical species loses electrons in a chemical reaction. It occurs when the oxidation number of a species increases.
A reduction reaction is defined as the reaction in which a chemical species gains electrons in a chemical reaction. It occurs when the oxidation number of a species decreases.
From the given ionic reactions:
[tex]Zn+Cu^{2+}\rightarrow Zn^{2+}+Cu[/tex]
On the reactant side:
Oxidation number of Zn = 0
Oxidation number of Cu = +2
On the product side:
Oxidation number of Cu = 0
Oxidation number of Zn = +2
As the oxidation number of Zn is increasing from 0 to +2. Thus, it is getting oxidized. Similarly, the oxidation number of Cu is decreasing from +2 to 0. Thus, it is getting reduced. Therefore, forming a redox couple
Hence, the correct option is D. [tex]Zn+Cu^{2+}\rightarrow Zn^{2+}+Cu[/tex]
An opening volumetric cylinder filled with water at volume 0.003m after period of
time the water in the cylinder is just evaporated what is the work done by this process?
Answer:
= - 303.975 Joules
Explanation:
Given that:
The volume of the cylinder = 0.003 m^3
Now, to liters:
The volume = 0.003 *1000 L
= 3 L
For an open cylinder, we mean the atmospheric pressure is at standard condition.
Thus, the workdone = -PΔV
= - 1 atm (3 L)
= - 3 L atm
1 L atm to Joules
= 101.325 Joules
Therefore;
=- 3* 101.325 Joules
= - 303.975 Joules
What type of nuclear decay is shown by the reaction below?
A. Alpha
B. Gamma
C. Beta
O D. Fission
Answer:
C. Beta
Explanation:
HELP WILL GIVE BRAINLIEST!!
Using the following reaction, calculate the percent yield of CaO if 20.4g of CaCO3 are heated and 10.6g of CaO are actually produced
CaCO3(s) → CaO(s) + CO2(g)
Answer:
92.79%
Explanation:
The Molar mass :
Molar mass of CaC03 = (40 + 12 + (16*3)) = 100 g/mol
Molar mass of Ca0 = (40 + 16) = 56 g/mol
Theoretical yield :
20.4g CaCO3 * 56g Ca0 / 100g CaCO3
= (20.4 * 56)/100 = 11.424 CaO
The actual yield Given is : 10.6g Ca0
The percentage yield is given by :
% yield = Actual yield / theoretical yield
% yield = 10.6 g / 11.424 g * 100%
% yield = 0.9278711 * 100%
Percentage yield = 92.79%
which compounds are an alkanes, CnH2n+2? pls reply fast!
Answer:
Methane
Explanation:
Alkanes have the molecular formula of "CnH2n+2" which means for every carbon molecule there are two hydrogens plus two more. For example when there is one Carbon there are four hydrogens, this molecule is known as "Methane"
Given the reaction:
Sn2+ (aq) + 2Fe3+ (aq) → Sn4+ (aq) + 2Fe2+ (aq)
The oxidizing agent in this reaction is?
A Sn2+
B Fe3+
C Sn4+
D Fe2+