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3 years ago

What is true of experimental designs that are used in scientific research?

Chemistry

1 answer:

MissTica3 years ago

3 0

This is used for multiple scientists can perform the experiment and they can compare results.
Hope This Helps! :D

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Uranium-238 decays to lead-206 with a half-life of 4.5 x 109 yr. Determine how much uranium-238 decays in milligrams (to three s

Mamont248 [21]

Answer:

2.15 mg of uranium-238 decays

Explanation:

For decay of radioactive nuclide-

$N=N_{0}.(\frac{1}{2})^{\frac{t}{t_{\frac{1}{2}}}}$

where N is amount of radioactive nuclide after t time, $N_{0}$ is initial amount of radioactive nuclide and $t_{\frac{1}{2}}$ is half life of radioactive nuclide

Here $N_{0}=4.60 mg$ , $t=4.1\times 10^{9}yr$ and $t_{\frac{1}{2}}=4.5\times 10^{9}yr$

So, $N=(4.60mg)\times (\frac{1}{2})^{\frac{4.1\times 10^{9}}{4.5\times 10^{9}}}$

so, N = 2.446 mg

mass of uranium-238 decays = (4.60-2.446) mg = 2.15 mg

3 0

3 years ago

20. What is the area of a piece of metal foil that measures 43.9 cm by 29.21 cm? Express the answer to

Aneli [31]

Answer:

The correct answer is b. 1280 cm^2

4 0

3 years ago

This download is my science worksheet. It's about different types of energy in a situation, like examples. btw this is 7th grade

scoray [572]

All types of energy can be resumed into two basic types of energy which include kinetic energy and potential energy.

<h3>What is kinetic energy?</h3>

Energy is the ability to perform a given work. Kinetic energy is energy in movement, whereas potential energy is stored energy.

For example, plant photosynthesis makes reference to chemical energy (potential energy), popcorn makes reference to thermal energy, etc.

In conclusion, all types of energy can be resumed into two basic types of energy which include kinetic energy and potential energy.

Learn more about kinetic energy here:

brainly.com/question/25959744

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8 0

2 years ago

The specific rotation of (S)-2-butanol is +13.5. If 0.119 g of its enantiomer is dissolved in 10.0 mL of ethanol and

larisa86 [58]

Answer:

+15.8°

Explanation:

The formula for the observed rotation (α) of an optically active sample is

α = [α]<em>lc </em>

where

<em>l</em> = the cell path length in decimetres

<em>c</em> = the concentration in units of g/100 mL

[α] = the specific rotation in degrees

1. Convert the concentration to units of g/100 mL

$c = \frac{\text{0.119 g}}{\text{10.0 mL}} \times \frac{10 }{10 } =\frac{\text{1.19 g}}{\text{100 mL}}$

2. Calculate the observed rotation

$\alpha = (+13.3 ^{\circ}) \times 1.19 \times 1 = +15.8^{\circ}$

7 0

3 years ago

A substance decays so that the amount a of the substance left at time t is given by: a = a0 ∙ (0.8)t where a0 is the original am

Zolol [24]

The half-life of the substance is 3.106 years.

<h3>What is the formula for exponential decay?</h3>

The exponential decline, which is a rapid reduction over time, can be calculated with the use of the exponential decay formula.
The exponential decay formula is used to determine population decay, half-life, radioactivity decay, and other phenomena.
The general form is F(x) = a.

Here,

a = the initial amount of substance

1-r is the decay rate

x = time span

The equation is given in its correct form as follows:

a = $a_{0}$ × $(0.8)^{t}$

As this is an exponential decay of a first order reaction, t is an exponent of 0.8.

Now let's figure out the half life. Since the amount left is half of the initial amount at time t, that is when:

a = 0.5 a0

<h3>Substituting this into the equation:</h3>

0.5 $a_{0}$ = $a_{0}$ × $(0.8)^{t}$

0.5 = $(0.8)^{t}$

taking log on both sides

t log 0.8 = log 0.5

t = log 0.5/log 0.8

t = 3.106 years

The half-life of the substance is 3.106 years.

To learn more about exponential decay formula visit:

brainly.com/question/28172854

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4 0

1 year ago