Lots of substances. Rocks, metals, minerals, you name it.
<h3>
Answer:</h3>
1.2 × 10⁻⁸ mol Pb
<h3>
General Formulas and Concepts:</h3>
<u>Math</u>
<u>Pre-Algebra</u>
Order of Operations: BPEMDAS
- Brackets
- Parenthesis
- Exponents
- Multiplication
- Division
- Addition
- Subtraction
<u>Chemistry</u>
<u>Atomic Structure</u>
- Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.
<u>Stoichiometry</u>
- Using Dimensional Analysis
<h3>
Explanation:</h3>
<u>Step 1: Define</u>
[Given] 7.2 × 10¹⁵ atoms Pb
<u>Step 2: Identify Conversions</u>
Avogadro's Number
<u>Step 3: Convert</u>
- [DA] Set up:
![\displaystyle 7.2 \cdot 10^{15} \ atoms \ Pb(\frac{1 \ mol \ Pb}{6.022 \cdot 10^{23} \ atoms \ Pb})](https://tex.z-dn.net/?f=%5Cdisplaystyle%207.2%20%5Ccdot%2010%5E%7B15%7D%20%5C%20atoms%20%5C%20Pb%28%5Cfrac%7B1%20%5C%20mol%20%5C%20Pb%7D%7B6.022%20%5Ccdot%2010%5E%7B23%7D%20%5C%20atoms%20%5C%20Pb%7D%29)
- [DA] Multiply/Divide [Cancel out units]:
![\displaystyle 1.19562 \cdot 10^{-8} \ mol \ Pb](https://tex.z-dn.net/?f=%5Cdisplaystyle%201.19562%20%5Ccdot%2010%5E%7B-8%7D%20%5C%20mol%20%5C%20Pb)
<u>Step 4: Check</u>
<em>Follow sig fig rules and round. We are given 2 sig figs.</em>
1.19562 × 10⁻⁸ mol Pb ≈ 1.2 × 10⁻⁸ mol Pb
Answer:
![\%m/m=14\%](https://tex.z-dn.net/?f=%5C%25m%2Fm%3D14%5C%25)
Explanation:
Hello!
In this case, since the molarity of magnesium chloride (molar mass = 95.211 g/mol) is 1.672 mol/L and we know the density of the solution, we can first compute the concentration in g/L as shown below:
![[MgCl_2]=1.672\frac{molMgCl_2}{L}*\frac{95.211gMgCl_2}{1molMgCl_2}=159.2\frac{gMgCl_2}{L}](https://tex.z-dn.net/?f=%5BMgCl_2%5D%3D1.672%5Cfrac%7BmolMgCl_2%7D%7BL%7D%2A%5Cfrac%7B95.211gMgCl_2%7D%7B1molMgCl_2%7D%3D159.2%5Cfrac%7BgMgCl_2%7D%7BL%7D)
Next, since the density of the solution is 1.137 g/mL, we can compute the concentration in g/g as shown below:
![[MgCl_2]=159.2\frac{gMgCl_2}{L}*\frac{1L}{1000mL}*\frac{1mL}{1.137g}=0.14](https://tex.z-dn.net/?f=%5BMgCl_2%5D%3D159.2%5Cfrac%7BgMgCl_2%7D%7BL%7D%2A%5Cfrac%7B1L%7D%7B1000mL%7D%2A%5Cfrac%7B1mL%7D%7B1.137g%7D%3D0.14)
Which is also the by-mass fraction and in percent it turns out:
![\%m/m=0.14*100\%\\\\\%m/m=14\%](https://tex.z-dn.net/?f=%5C%25m%2Fm%3D0.14%2A100%5C%25%5C%5C%5C%5C%5C%25m%2Fm%3D14%5C%25)
Best regards!