Ask question

Ask question

All categories

3 years ago

6

A teacher wants to perform a classroom demonstration that illustrates both chemical and physical changes. Which would be the bes

t demonstration that she could use?

1 answer:

Jlenok [28]3 years ago

5 0

when you crumble paper is still paper when you burn down paper you get ashes. that is want is call chemical and physical changes.

You might be interested in

Explain why food chains do not tend to exceed four links.

Softa [21]

Energy is "lost" at each trophic level when you go up the chain. <span> Typically there are fewer organisms at higher trophic levels.

Hope this helps!</span>

3 0

3 years ago

If a sample of gas is located 10.2 cm from the injection point and the chart speed is 0.5 cm/min, what is the retention time?

Archy [21]

Answer : The retention time is, 20 min

Explanation :

Retention time : It is defined as the amount of time a compound spends on the column after it has been injected.

Formula of retention time is:

$\text{Retention time}=\frac{\text{Distance from injection point to center of peaks}}{\text{Chart recorded speed}}$

Given:

Distance from injection point to center of peaks = 10 cm

Chart recorded speed = 0.5 cm/min

Now put all the given values in the above formula, we get:

$\text{Retention time}=\frac{10cm}{0.5cm/min}$

Retention time = 20 min

Thus, the retention time is, 20 min

3 0

4 years ago

Calculate the standard free-energy change at 25 ∘C for the following reaction:

lianna [129]

Answer:

Standard free-energy change at $25^{0}\textrm{C}$ is $-3.80\times 10^{2}kJ/mol$

Explanation:

Oxidation: $Mg(s)-2e^{-}\rightarrow Mg^{2+}(aq.)$

Reduction: $Fe^{2+}(aq.)+2e^{-}\rightarrow Fe(s)$

--------------------------------------------------------------------------------------

Overall: $Mg(s)+Fe^{2+}(aq.)\rightarrow Mg^{2+}(aq.)+Fe(s)$

Standard cell potential, $E_{cell}^{0}=E_{Fe^{2+}\mid Fe}^{0}-E_{Mg^{2+}\mid Mg}^{0}$

So, $E_{cell}^{0}=(-0.41V)-(-2.38V)=1.97V$

We know, standard free energy change at $25^{0}\textrm{C}$ ( $\Delta G^{0}$ ): $\Delta G^{0}=-nFE_{cell}^{0}$

where, n is number of electron exchanged during cell reaction, 1F equal to 96500 C/mol

Here n = 2

So, $\Delta G^{0}=-(2)\times (96500C/mol)\times (1.97V)=-380210J/mol=-380.21kJ/mol=-3.80\times 10^{2}kJ/mol$

8 0

3 years ago

Read 2 more answers

Why might a scientist repeat an experiment if he/she did not make a mistake in the first one? An experiment should be repeated t

makvit [3.9K]

The answer is C. To ensure the results are accurate.

5 0

3 years ago

Read 2 more answers

Which choice BEST describes the motion of the car represented by the graph?

yanalaym [24]

the gas it has in it. it’s moving because of the gas

4 0

3 years ago