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jarptica [38.1K]
3 years ago
14

What event marks the beginning of Earth's current era?

Chemistry
2 answers:
Firlakuza [10]3 years ago
4 0
It’s B a mass extinction

uysha [10]3 years ago
3 0
B. We are in the cenzoic era so what previously had happen to cause the life we live today was a huge mass extinction.... hope this helps!!
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Among animals, what is one major advantage of sexual reproduction compared to asexual reproduction?
zimovet [89]
D: they have new dna combinations
5 0
3 years ago
I NEED HELP PLEASEEEEEE I WILL RATE BRAINLIEST!!!!
MrRa [10]
<span>0.002 moles is the answer </span>
8 0
3 years ago
The is the si unit that expresses the amount of substance. Specifically, it is defined as the amount of substance containing the
Dmitry_Shevchenko [17]

The <u>Mole</u> is the SI unit that expresses the amount of substance.

Mole is defined as - The mole is the amount of substance containing the same number of entities as there are in the 12 grams of Carbon - 12.

Mole is denoted by using symbol mol.

      Mole = 6.022 x 10²³ elementary entities.

These number of elementary entities in 1 mole is equal to or called as an Avogadro's number.  Mole is equal to 6.022 x 10²³ because this number of entity is same as in exactly 12 g of carbon-12.

It is a very important SI unit of measured which is used by the chemists. Moles are used in measuring in small or tiny things such as atoms, molecules and the other tiny particles.

To learn more about the mole concept,

brainly.com/question/28498715

#SPJ4

3 0
1 year ago
A sample of nitrogen gas is stored in a 489.6 mL flask at 108 kPa and 10.0°C. The gas is transferred to a 750.0 mL flask at 28.7
Wewaii [24]

Answer:

P2= 125.26 Kpa

Explanation:

V1= 489.6 ml=0.4896L

V2= 750 ml= 0.750L

V1= 180 KPa= 180000 Pa

P2= ?

T1= 10 = 10 + 273.15 = 283.15K

T2= 28.7+273.15= 301.85K

180000Pa* 0.4896L/ 283.15K * 301.85K/0.75L

P2= 12526.28553

P2= 125.26 KPa

5 0
3 years ago
A certain radioactive isotope decays at a rate of 0.2​% annually. Determine the ​half-life of this​ isotope, to the nearest year
pychu [463]

Answer:

The half-life of the radioactive isotope is 346 years.

Explanation:

The decay rate of the isotope is modelled after the following first-order linear ordinary differential equation:

\frac{dm}{dt} = -\frac{m}{\tau}

Where:

m - Current isotope mass, measured in kilograms.

t - Time, measured in years.

\tau - Time constant, measured in years.

The solution of this differential equation is:

m(t) = m_{o}\cdot e^{-\frac{t}{\tau} }

Where m_{o} is the initial mass of the isotope. It is known that radioactive isotope decays at a yearly rate of 0.2 % annually, then, the following relationship is obtained:

\%e = \frac{m(t)-m(t+1)}{m(t)}\times 100\,\% = 0.2\,\%

1 - \frac{m(t+1)}{m(t)} = 0.002

1 - \frac{m_{o}\cdot e^{-\frac{t+1}{\tau} }}{m_{o}\cdot e^{-\frac{t}{\tau} }}=0.002

1 - e^{-\frac{1}{\tau} } = 0.002

e^{-\frac{1}{\tau} } = 0.998

-\frac{1}{\tau} = \ln 0.998

The time constant associated to the decay is:

\tau = -\frac{1}{\ln 0.998}

\tau \approx 499.500\,years

Finally, the half-life of the isotope as a function of time constant is given by the expression described below:

t_{1/2} = \tau \cdot \ln 2

If \tau \approx 499.500\,years, the half-life of the isotope is:

t_{1/2} = (499.500\,years)\cdot \ln 2

t_{1/2}\approx 346.227\,years

The half-life of the radioactive isotope is 346 years.

6 0
3 years ago
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