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3 years ago

What is freezing point in science ?

1 answer:

4 0

We have all been taught that water freezes at 32 degrees Fahrenheit, 0 degrees Celsius, 273.15 Kelvin. That's not always the case, though. Scientists have found liquid water as cold as -40 degrees F in clouds and even cooled water down to -42 degrees F in the lab.

Here ya go.

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HELPPPPPPPPPPPPPPPPPPPP MEEEEEEEEEEEEEEEE PLZZZZZ WITHHHHH SCIENCE 13. Evaluate: What type of bonding does a material most likel

djyliett [7]

13 An Ionic Bond

these are the characteristics of an ionic bond compounds like NaCl have these characteristics

14 substances could be compounds or elements hence not all substances are compounds

15 It is not water. The chemical composition of water is H2O not H202

(H202 is hydrogen peroxide and is toxic)

6 0

3 years ago

Be sure to answer all parts. Nitric oxide, NO·, is a radical thought to cause ozone destruction by a mechanism similar to that o

SIZIF [17.4K]

Answer:

See image attached and explanation

Explanation:

The stratospheric ozone layer is very important in absorbing high-energy ultraviolet radiation that is harmful to living systems on earth. The concentration of ozone in the stratosphere is determined by both thermal and photochemical pathways for its decomposition. Nitric oxide, NO, is a trace constituent in the stratosphere that reacts with ozone to form nitrogen dioxide, NO2, and the diatomic oxygen molecule. The nitrogen-oxygen bond in NO2 is relatively weak. When an NO2 molecule encounters an oxygen atom, it transfers an oxygen, forming O2 and NO. The chemical reactions involved are formations of NO2 following by reaction of NO2 with atomic oxygen for form NO and O2. The sum of both reactions show that the overall reaction is simply the reaction of ozone with atomic oxygen to form two molecules of molecular oxygen. Hence, NO only serves as a catalyst, it does not undergo a permanent change itself.

6 0

3 years ago

Predict the sign of ΔSsys for each process: (b) A solid explosive converts to a gas.

Goryan [66]

The sign of ΔSsys for a solid explosive converts to a gas is positive.

The term used for the measurement of randomness and disorderliness in a system is known as Entropy (S). ΔS calculates the change in entropy and it is positive when entropy increase and negative when entropy decreases.

Entropy increases when heat is added to the system. Addition of heat increases the randomness of the molecules and hence the entropy increases.

When a solid explosive converts to a gas the randomness increases. Explosive causes heat and the solid is converted into gas. The randomness of molecules is maximum in gases thus the entropy increases. The sign of ΔS is positive for this process.

If you need to learn more about the signs of ΔSsys, click here

brainly.com/question/14250855

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7 0

2 years ago

The initial reaction rate for the elementary reaction 2A + B → 4C was measured as a function of temperature when the concentrati

Artist 52 [7]

Complete Question

The complete question is shown on the first uploaded image

Answer:

a) The activation energy is 124.776 $\frac{kJ}{mole}$

b) The frequency factor is 1.77 × $10^{18}$

c) The rate constant is 0.00033 $(\frac{dm^{3} }{mole} )^{2}$ $\frac{1}{s}$

Explanation:

From the question the elementary reaction for A and B is given as

2A + B → 4C

The rate equation the elementary reaction is

- $r_{A}$ = $k$ $[A]^{2}$ $[B]$

= $k[2]^{2}[1.5]$

= 6k

$k = \frac{-r_{A} }{6}$

When temperature changes, the rate constant change an this causes the rate of reaction to change as shown on the second uploaded image.

The relationship between temperature and rate constant can be deduced from these equation

$k = Aexp(-\frac{E_{a} }{RT} )$

taking ln of both sides we have

$lnk =ln A - (\frac{E_{a} }{R}) \frac{1}{T}$

Considering the graph for the rate constant $ln k$ and $(\frac{1}{T} )$ the slope from the equation is $-(\frac{E_{a} }{R})$ and the intercept is $ln A$

From the given table we can generate another table using the equation above as shown on the third uploaded image

The graph of $ln k$ vs $(\frac{1}{T} )$ is shown on the fourth uploaded image

From the graph we can see that the slope is $-(\frac{E_{a} }{R} ) = - 15008$

Now we can obtain the activation energy $E_{a}$ by making it the subject in the equation also generally R which is the gas constant is $8.145 \frac{J}{kmole}$