Question

how many moles are present in 45.7 cm³ of chromium (cr), given that the density of chromium is 7.192 g/cm³. how many moles are present in 25.00 ml of mercury, given that the specific gravity of mercury is 13.633. 2.4 the periodic table define the following: periods groups metals properties of metals: nonmetals properties of nonmetals: metalloids properties of metalloids:

Explanation:

First Calculation Problem: Moles of Chromium

Step1: Calculate mass of Cr

Mass = Density × Volume
$m = 7.192\ \text{g/cm}^3 \times 45.7\ \text{cm}^3 = 328.6744\ \text{g}$

Step2: Find molar mass of Cr

Molar mass of Cr = $52.00\ \text{g/mol}$

Step3: Calculate moles of Cr

Moles = $\frac{\text{Mass}}{\text{Molar Mass}}$
$n = \frac{328.6744\ \text{g}}{52.00\ \text{g/mol}} \approx 6.32\ \text{mol}$

Step1: Convert specific gravity to density

Density of Hg = $13.633\ \text{g/mL}$ (since specific gravity = density relative to water, $1\ \text{g/mL}$)

Step2: Calculate mass of Hg

Mass = Density × Volume
$m = 13.633\ \text{g/mL} \times 25.00\ \text{mL} = 340.825\ \text{g}$

Step3: Find molar mass of Hg

Molar mass of Hg = $200.59\ \text{g/mol}$

Step4: Calculate moles of Hg

Moles = $\frac{\text{Mass}}{\text{Molar Mass}}$
$n = \frac{340.825\ \text{g}}{200.59\ \text{g/mol}} \approx 1.70\ \text{mol}$

• Periods: Horizontal rows on the periodic table, corresponding to the principal quantum number (energy level) of valence electrons.
• Groups: Vertical columns on the periodic table; elements in the same group have identical valence electron configurations and similar chemical properties.
• Metals: Elements that typically lose electrons in chemical reactions, located on the left and middle of the periodic table.
• Properties of metals: Good conductors of heat/electricity, malleable, ductile, have high melting/boiling points, and form positive ions (cations).
• Nonmetals: Elements that typically gain or share electrons in reactions, located on the right side of the periodic table.
• Properties of nonmetals: Poor conductors of heat/electricity, brittle, have low melting/boiling points, and form negative ions (anions) or covalent compounds.
• Metalloids: Elements with properties intermediate between metals and nonmetals, found along the "staircase" dividing line of the periodic table.
• Properties of metalloids: Semiconductors of electricity, have a mix of metallic and nonmetallic physical/chemical traits (e.g., brittle but shiny).

Answer:

$\approx 6.32$ moles

---

Second Calculation Problem: Moles of Mercury