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Nitella [24]
3 years ago
7

How can we choose the best chemicals to create a cold or hot pack?

Chemistry
1 answer:
sergejj [24]3 years ago
6 0
<h3>♫ - - - - - - - - - - - - - - - ~Hello There!~ - - - - - - - - - - - - - - - ♫</h3>

➷ It would depend on whether they would create an endothermic reaction or exothermic. For a hot pack, the chemicals would need to release energy (heat). However, a cold pack would need chemicals that need to draw heat from the surroundings to produce a cool sensation.

<h3><u>✽</u></h3>

➶ Hope This Helps You!

➶ Good Luck (:

➶ Have A Great Day ^-^

↬ ʜᴀɴɴᴀʜ ♡

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When cream mixes with coffee, is this a chemical or physical change?
svlad2 [7]

It is a physical change when cream mixes with coffee, it changes the color of the coffee. When you add more or less cream there is a color change depending on the consistency of cream. The properties are not changes and a no new compound is formed as in chemical change with a reaction of two compounds, a new compound is formed with different properties. So it is a physical change.

7 0
3 years ago
jalyn ran at speed of 3 m/s then came to a sudden stop during a time period of 3 s. what was his acceleration​
tensa zangetsu [6.8K]

Answer:

I believe the answer is 1m/s²

Explanation:

acceleration= change in speed ÷ time (I hope this is correct)

4 0
4 years ago
. If this same atom with 22 protons and 19 electrons were to gain 3 electrons, the net charge on the atom would be
mina [271]

Answer:

neutral

Explanation:

19+3=22

22 protons & 22 neutrons --> neutral net charge

3 0
3 years ago
How acidic buffer resist change in pH on addition of acid and base.
andrew-mc [135]

Answer:

Buffers are solutions that resist changes in pH, upon addition of small amounts of acid or base. The can do this because they contain an acidic component, HA, to neutralize OH- ions, and a basic component, A-, to neutralize H+ ions. Since Ka is a constant, the [H+] will depend directly on the ratio of [HA]/[A-].

hope it's help

<h3>#carryONlearning </h3>
5 0
3 years ago
The activation energy for a reaction is changed from 184 kJ/mol to 59.0 kJ/mol at 600. K by the introduction of a catalyst. If t
11111nata11111 [884]

Answer:

The catalyzed reaction will take 2.85 seconds to occur.

Explanation:

The activation energy of a reaction is given by:                                                        

k = Ae^{-\frac{E_{a}}{RT}}

For the reaction without catalyst we have:

k_{1} = Ae^{-\frac{E_{a_{1}}}{RT}}   (1)

And for the reaction with the catalyst:

k_{2} = Ae^{-\frac{E_{a_{2}}}{RT}}   (2)

Assuming that frequency factor (A) and the temperature (T) are constant, by dividing equation (1) with equation (2) we have:                      

\frac{k_{1}}{k_{2}} = \frac{Ae^{-\frac{E_{a_{1}}}{RT}}}{Ae^{-\frac{E_{a_{2}}}{RT}}}

\frac{k_{1}}{k_{2}} = e^{\frac{E_{a_{2}} - E_{a_{1}}}{RT}    

\frac{k_{1}}{k_{2}} = e^{\frac{59.0 \cdot 10^{3}J/mol - 184 \cdot 10^{3} J/mol}{8.314 J/Kmol*600 K} = 1.31 \cdot 10^{-11}    

Since the reaction rate is related to the time as follow:

k = \frac{\Delta [R]}{t}

And assuming that the initial concentrations ([R]) are the same, we have:

\frac{k_{1}}{k_{2}} = \frac{\Delta [R]/t_{1}}{\Delta [R]/t_{2}}

\frac{k_{1}}{k_{2}} = \frac{t_{2}}{t_{1}}

t_{2} = t_{1}\frac{k_{1}}{k_{2}} = 6900 y*1.31 \cdot 10^{-11} = 9.04 \cdot 10^{-8} y*\frac{365 d}{1 y}*\frac{24 h}{1 d}*\frac{3600 s}{1 h} = 2.85 s

Therefore, the catalyzed reaction will take 2.85 seconds to occur.

I hope it helps you!                            

4 0
3 years ago
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