Answer:
The correct options are:
1) Pure chemical substance
2) Element.
Explanation:
each of the term is explained below:
1) <u>Mixture: </u> Since tungsten is an element in periodic table thus it is not a mixture.
2) False by definition of mixture.
3) false by definition of mixture.
4) <u>Solution:</u> Tungsten in a filament is in solid form hence solution is incorrect.
5) Since it is given in the question itself that the sample is pure hence option 'E' is correct as chemical substance is a pure substance that has a homogeneous composition and the sample in the question is given as pure.
6) <u>Compound:</u> By definition of compound it is formed by mixing 2 or more elements but since tungsten is an element that occurs independently in nature hence it is not a compound.
7) Tungsten is a element in the periodic table with atomic number 74.
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:
Examples of substances insoluble in water: oil, acetone, ether
Explanation:
Such examples of substances are non-polar and do not dissolve in water (polar compound). The classic example is oil floating in water (this happens because oil has a lower density than water).
It’s the greenhouse effect. Hope this helps!
Answer:
pOH = 5.961
Explanation:
To find the pH of a weak base we can use Henderson-Hasselbalch equation for weak bases:
pOH = pKb + log [(CH₃)₃NHCl] / [(CH₃)₃N]
<em>Where pKb is -log Kb = 4.187 and [] could be taken as moles of each specie.</em>
<em />
<em>Moles (CH₃)₃NHCl:</em>
0.0441L * (0.15mol/L) = 6.615x10⁻³moles
<em>Moles (CH₃)₃N:</em>
0.0233L * (0.16mol/L) = 3.728x10⁻³moles
And pOH is:
pOH = pKb + log [(CH₃)₃NHCl] / [(CH₃)₃N]
pOH = 4.187 + log [6.615x10⁻³moles] / [3.728x10⁻³moles]
<h3>pOH = 5.961</h3>
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