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yuradex [85]
3 years ago
7

which is a scientific claim? At least 75 percent of the class will pass the physical science test today because they studied mor

e than two hours for it. According to the star of the number-one teen TV show, crushed rosemary and olive oil spread over pimples will draw out the bacteria and prevent scarring. Plants fertilized once per week with Super Plant Food Formula have been shown in testing to produce twice as much fruit as plants that are not. Placing half-filled one-gallon jugs of water out on the lawn prevents moles from occupying the space underground.
Chemistry
2 answers:
wlad13 [49]3 years ago
3 0
Plants fertilized one per week with Super Plant Food Formula have been shown in testing to produce twice as much fruit as plants that are not. 

That answer is the most scientific because it states the word "testing" and in science they do a bunch of test to make a scientific claim. 
kolezko [41]3 years ago
3 0
The correct answer is C. I took this test.
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A student dissolves 15.0 g of ammonium chloride(NH4Cl) in 250. 0 g of water in a well-insulated open cup. She then observes the
iren2701 [21]

Answer:  

1) Endothermic.  

2) Q_{rxn}=4435.04J  

3) \Delta _rH=15.8kJ/mol

Explanation:  

Hello there!  

1) In this case, for these calorimetry problems, we can realize that since the temperature decreases the reaction is endothermic because it is absorbing heat from the solution, that is why the temperature goes from 22.00 °C to 16.0°C.  

2) Now, for the total heat released by the reaction, we first need to assume that all of it is released by the solution since it is possible to assume that the calorimeter is perfectly isolated. In such a way, it is also valid to assume that the specific heat of the solution is 4.184 J/(g°C) as it is mostly water, therefore, the heat released by the reaction is:

Q_{rxn}=-(15.0g+250.0g)*4.184\frac{J}{g\°C}(16.0-20.0)\°C\\\\ Q_{rxn}=4435.04J    

3) Finally, since the enthalpy of reaction is calculated by dividing the heat released by the reaction over the moles of the solute, in this case NH4Cl, we proceed as follows:

\Delta _rH=\frac{ Q_{rxn}}{n}\\\\\Delta _rH= \frac{ 4435.04J}{15.0g*\frac{1mol}{53.49g} } *\frac{1kJ}{1000J} \\\\\Delta _rH=15.8kJ/mol

Best regards!  

Best regards!

4 0
2 years ago
What are some physical means of separating something?
Alika [10]
Mixtures come in many forms and phases. Most of them can be separated, and the kind of separation method depends on the kind of mixture it is. Below are some common separation methods:
3 0
2 years ago
g A microwave oven heats by radiating food with microwave radiation, which is absorbed by the food and converted to heat. If the
Sliva [168]

Answer:

The total photons required = 5.19 × 10²⁸ photons

Explanation:

Given that:

the radiation wavelength λ= 12.5 cm = 0.125 m

Volume of the container = 0.250 L = 250 mL

The density of water = 1 g/mL

Density = mass /volume

Mass =  Volume ×  Density

Thus; the mass of the water =  250 mL ×  1 g/mL

the mass of the water = 250 g

the specific heat of water s = 4.18 J/g° C

the initial temperature T_1 = 20.0° C

the final temperature T_2 = 99° C

Change in temperature \Delta T = (99-20)° C = 79 ° C

The heat q absorbed during the process = ms \Delta T

The heat q absorbed during the process = 250 g × 4.18 J/g° C × 79° C

The heat q absorbed during the process = 82555 J

The energy of a photon can be represented by the equation :

= hc/λ

where;

h = planck's constant = 6.626 \times 10^{-34} \ J.s

c = velocity of light = 3.0 \times 10^8 \ m/s

=  \dfrac{6.626 \times 10^{-34} \times 3.0 \times 10^8}{0.125}

= 1.59024 \times 10^{-24} J

The total photons required = Total heat energy/ Energy of a photon

The total photons required = \dfrac{82555 J}{1.59024 \times 10^{-24}J}

The total photons required = 5.19 × 10²⁸ photons

5 0
2 years ago
The half-life of nitrogen-13 is 10.0 minutes. if you begin with 53.3 mg of this isotope, what mass remains after 25.9 minutes ha
zimovet [89]

Hello!

The half-life is the time of half-disintegration, it is the time in which half of the atoms of an isotope disintegrate.

We have the following data:

mo (initial mass) = 53.3 mg

m (final mass after time T) = ? (in mg)

x (number of periods elapsed) = ?

P (Half-life) = 10.0 minutes

T (Elapsed time for sample reduction) = 25.9 minutes

Let's find the number of periods elapsed (x), let us see:

T = x*P

25.9 = x*10.0

25.9 = 10.0\:x

10.0\:x = 25.9

x = \dfrac{25.9}{10.0}

\boxed{x = 2.59}

Now, let's find the final mass (m) of this isotope after the elapsed time, let's see:

m =  \dfrac{m_o}{2^x}

m =  \dfrac{53.3}{2^{2.59}}

m \approx \dfrac{53.3}{6.021}

\boxed{\boxed{m \approx 8.85\:mg}}\end{array}}\qquad\checkmark

I Hope this helps, greetings ... DexteR! =)

3 0
2 years ago
Atoms with loosely held valence electrons have 1. high ionization energy and high electron affinity. 2. high ionization energy a
EastWind [94]

Answer:

4

Explanation:

Ionization energy can be defined as the energy required for an atom to lose its valence electron to form an ion. Hence, it deals with how easily an atom would lose its electron and form an ion. As the valence electrons are lossless bound to the outermost shell, they can easily be lost without much problem or better still they can be lost easily. Hence, the energy change here is small and thus we can conclude that the ionization energy here is low.

The electron affinity works quite differently from the ionization energy. It deals with the way in which a neutral atom attracts an electron to form an ion. For an electron with loose valence electrons, the sure fact is that it does not really need these electrons. Hence, there is no need for an high electron affinity on its part. Thus, we conclude that the electron affinity is also low

3 0
3 years ago
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