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4 years ago

HELP When a scientist thinks of a reason for why he or she observed something, this reason is called _______.

Chemistry

2 answers:

bonufazy [111]4 years ago

6 0

Answer:

Explanation:

they are inferring a reason as to why something happened, everything else has already happened, except the test, which will occur to test the inference

nydimaria [60]4 years ago

3 0

Answer:

an inference

Explanation:

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The radioactive isotope of lead, Pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.

Marina86 [1]

Answer:

Therefore it will take 7.66 hours for 80% of the lead decay.

Explanation:

The differential equation for decay is

$\frac{dA}{dt}= kA$

$\Rightarrow \frac{dA}{A}=kdt$

Integrating both sides

ln A= kt+c₁

$\Rightarrow A= e^{kt+c_1}$

$\Rightarrow A=Ce^{kt}$ [ $e^{c_1}=C$ ]

The initial condition is A(0)= A₀,

$\therefore A_0=Ce^{0.k}$

$\Rightarrow C=A_0$

$\therefore A=A_0e^{kt}$ .........(1)

Given that the $Pb_{209}$ has half life of 3.3 hours.

For half life $A=\frac12 A_0$ putting this in equation (1)

$\frac12A_0=A_0e^{k\times3.3}$

$\Rightarrow ln(\frac12)= 3.3k$ [taking ln both sides, $ln \ e^a=a$ ]

$\Rightarrow k=\frac{ln \frac12}{3.3}$

⇒k= - 0.21

Now A₀= 1 gram, 80%=0.8

and A= (1-0.8)A₀ = (0.2×1) gram = 0.2 gram

Now putting the value of k,A and A₀in the equation (1)

$\therefore 0.2=1e^{(-0.21)\times t}$

$\Rightarrow e^{-0.21t}=0.2$

$\Rightarrow -0.21t= ln(0. 2)$

$\Rightarrow t= \frac{ln (0.2)}{-0.21}$

⇒ t≈7.66

Therefore it will take 7.66 hours for 80% of the lead decay.

3 0

3 years ago

Describe all the relationships between pressure, volume, and temperature

hammer [34]

The pressure of a given amount of gas is directly proportional to its absolute temperature, provided that the volume does not change (Amontons's law).

 The volume of a given amount of gas is inversely proportional to its pressure when temperature is held constant (Boyle's law).

3 0

3 years ago

Read 2 more answers

How would having too much sample in the melting point tube most likely affect the melting point measurement? Select the correct

oksano4ka [1.4K]

Answer:

2-4 mm height of capillary tube.

Explanation:

Sample should be around 2-4 mm in height.

It should be packed well so that it does not have air packets that caues the lowering of melting point.

If you take greater amount, then there will be needed more heat, resulting a wide range of melting point.

7 0

3 years ago

Uranium has an atomic number of 92. How many neutrons does U-238 have?

LekaFEV [45]

Answer:

146 neutrons.

Explanation:

8 0

3 years ago

Suppose a fox population exists in an ecosystem. Some of the foxes maintain a heavy coat year-round, while others shed their hea

algol [13]

Answer:

The fox who shed their heavy coat in the summer.

Explanation:

If a fox has the ability to shed its coat in the summer, it will have no difficulties adapting to new temperatures even during winter. However, the heavy-coated one will.

4 0

3 years ago