I think the best answer that will describe chemical change is the first option. During a chemical change, b<span>oth the identity and the properties of a substance change because new substances are being formed by a chemical reaction. An example is rusting of steel</span>
<span>I did some investigation and summarized the process and made a clearer explanation so those who are confused can imagine the process better :) A scientific theory attempts to explain and describe why things happen. Hypotheses are formed and experiments are done to validate or toss the hypothesis based on the data collected. The Atomic Theory has gone through lots of refining as a scientific theory. For instance, William Crookes conduced an experiment with cathode ray tubes powered by electricity that glowed when powered. Crookes placed an object in between the positive and negative electrode and concluded that the shadow made on the positive side was small particles of matter traveling from the negative side. But more evidence was needed so, later on, J.J. Thomson continued Crookes experiment. He tested what would happen if a negative or positive charged rod was placed along the ray tubes and if it would differ if a different element was used as the negative electrode. Thomson found out that the beam had negatively charged particles and that even if the negative electrode is substituted, the glow is still present, meaning that all elements also had the small negative particles. These particles(now known as electrons) were smaller than the atom and were added to the model of the atom dispersed throughout the neutrally charged atom inside its positive sphere. Now came along Rutherford hoping to support Thomsons model by firing positively charged particles at a thin gold foil thinking it would go straight through the foil, but instead it evenly distributed as they went through the foil, concluding that atoms have a small, dense nucleus(containing positive protons and most of the mass of the atom) that deflected the particles passing through. This was a drastic change in the model now knowing that 1 proton has 2000 times the mass of an electron, but its positive charge cancels the negative electron. After WW1, Chadwick and others were seeing that sometimes the mass of the atom was greater than the mass of the protons and the number of protons was less than the mass of the atom. So it was thought that there were extra electrons and protons adding mass in the nucleus but cancelling their charges, but Rutherford proposed a particle with mass but no charge and called it a neutron; made of paired protons and electrons. But scientists kept studying atoms since there was no evidence of the neutron. Chadwick repeated these experiments though, in hopes to find the neutron and succeeded in 1932, finding it in the nucleus with a close mass to the proton. Thanks to these experiments for refining a scientific theory, we now have a clearer model of the atom.</span>
<span>The student should
follow following steps to make 1 L of </span>2.0 M CaCl₂.<span>
<span>
1. First he should
calculate the number of moles of 2.0 M CaCl</span></span>₂ in 1 L solution.<span>
</span>Molarity of the solution = 2.0 M<span>
Volume of solution which should be prepared = 1 L
Molarity =
number of moles / volume of the solution
Hence, number of moles in 1 L = 2 mol
2. Find
out the mass of dry CaCl</span>₂ in 2 moles.<span>
moles =
mass / molar mass
Moles of CaCl₂ =
2 mol</span><span>
Molar mass of CaCl₂ = </span><span>110.98 g/mol
Hence, mass of CaCl</span>₂ = 2 mol x <span>110.98 g/mol
= 221.96
g
3. Weigh the mass
accurately
4. Then take a cleaned and dry1 L volumetric flask and place a funnel top of it. Then carefully add the salt into the volumetric flask and
finally wash the funnel and watch glass
with de-ionized water. That water also should be added into the volumetric
flask.
5. Then add some
de-ionized water into
the volumetric flask and swirl well until all salt are
dissolved.
<span>6. Then top up to
mark of the volumetric flask carefully.
</span></span>
7. As the final step prepared solution should be labelled.
Answer:
0.6257 M is the molarity of solution that is 5.50 percentage by mass oxalic acid.
Explanation:
Mass percentage of oxalic acid = 5.50%
This means that in 100 grams of solution there are 5.50 grams of oxalic acid.
Mass of solution , m = 100
Volume of the solution = V
Density of the solution = d = 1.024 g/mL
V = 97.66 mL = 0.09766 L
(1 mL = 0.001 L)
Moles of oxalic acid = 
The molarity of the solution :
0.6257 M is the molarity of solution that is 5.50 percentage by mass oxalic acid.
Hello.
The answer is: D it produces hyrogen ions in a solution.
This is correct because when Arrhenius acid it turns into hydrogen ions.substance as an acid if it produces hydrogen ions H(+) or hydronium ions in water. A substance is classified as a base if it produces hydroxide ions OH(-) in water.
have a nice day
