Considering the definition of percentage by mass, the mass percentage of CaCO₃ is 68.59%.
<h3>What is mass percentage</h3>
The percentage by mass expresses the concentration and indicates the amount of mass of solute present in 100 grams of solution.
In other words, the percentage by mass of a component of the solution is defined as the ratio of the mass of the solute to the mass of the solution, expressed as a percentage.
The percentage by mass is calculated as the mass of the solute divided by the mass of the solution, the result of which is multiplied by 100 to give a percentage. This is:

<h3>Mass percentage of CaCO₃</h3>
In this case, you know:
- mass of CaCO₃: 2.62 grams
- mass of limestone: 3.82 grams
Replacing in the definition of mass percentage:

<u><em>mass percentage= 68.59 %</em></u>
Finally, the mass percentage of CaCO₃ is 68.59%.
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Answer:
B. They are dimensionless ratios of the actual concentration or pressure divided by standard state concentration, which is 1 M for solutions and 1 bar for gases.
Explanation:
Activity of a substance is defined as the ratio of an effective concentration or an effective pressure to a standard state pressure or a standard state pressure. It is usually a unit less ratio.
Concentrations in an equilibrium constant are really dimensionless ratios of actual concentrations divided by standard state concentrations. Since standard states are 1 M for solutes, 1 bar for gases, and pure substances for solids and liquids, these are the units to be used.
Hence, activity is a fudge factor to ideal solutions that correct the true concentration. Activity of a gas and solute concentration is a ratio with no unit.
Answer:

Explanation:
Hello,
In this case, given the described concept regarding the Avogadro's number, we can easily notice that 27.0 g of aluminium foil has 6.022x10²³ atoms as shown below based on the mass-mole-particles relationship:

Notice this is backed up by the fact that aluminium molar mass if 27.0 g/mol.
Best regards.
We need to do some general algebra here.
We will find that you need 8.25 grams of CuNO₃ to make enough solution for the 22 labs.
<em>We know that:</em>
- Each lab group needs 25 ml of solution.
- it takes 15 g of CuNO₃ to make one L of that solution.
- There are 22 labs.
Because each lab needs 25 ml of solution, 22 labs will need that amount 22 times, so the <u>total amount of solution needed</u> is:
22*25ml = 550 ml
Now we know that we need 15 grams to make one liter of solution, and:
1 L = 1000ml
Then you need 15g to make 1000ml
and x (we want to find this amount) to make 550ml
Then we can write two equations (not actual equations, as these are different units) like:
x = 550ml
15g = 1000ml
Now we can take the quotient between these two equations:
x/15 g = (550ml/1000ml)
And now we can solve this for x:
x = (550ml/1000ml)*15g = 8.25g
So you need 8.25 grams of CuNO₃ to make enough solution for the 22 labs.
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Answer:
The answer is D.
Explanation:
Silver consists of 92.5% silver, and the remaining part is copper. ... Pure silver is not susceptible to tarnish in a pure oxygen environment. However, the copper that is contained in 925 sterling silver may react to the ozone and hydrogen sulfide in the air and cause sterling silver to tarnish.