The mineral magnetite is an iron oxide ore that has a density of $5.20 \mathrm{~g} / \mathrm{cm}^3$. At high temperature, magnetite reacts with carbon monoxide to yield iron metal and carbon dioxide. When $2.660 \mathrm{~g}$ of magnetite is allowed to react with sufficient carbon monoxide, the $\mathrm{CO}_2$ product is found to have a volume of $1.136 \mathrm{~L}$ at $298 \mathrm{~K}$ and $751 \mathrm{~mm} \mathrm{Hg}$ pressure.
(a) What mass of iron in grams is formed in the reaction?
(b) What is the formula of magnetite?
(c) Magnetite has a somewhat complicated cubic unit cell with an edge length of $839 \mathrm{pm}$. How many Fe and $\mathrm{O}$ atoms are present in each unit cell?

Iron is obtained commercially by the reaction of hematite $\left(\mathrm{Fe}_{2} \mathrm{O}_{3}\right)$ with carbon monoxide. How many grams of iron is produced when 25.0 mol of hematite reacts with 30.0 mol of carbon monoxide? $\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{s})+3 \mathrm{CO}(\mathrm{g}) \rightarrow 2 \mathrm{Fe}(\mathrm{s})+3 \mathrm{CO}_{2}(\mathrm{g})$

Use the table you prepared for previous problem to answer the following questions:

How would you distinguish between samples of copper (II) sulfate pentahydrate and iron (I) sulfate pentahydrate?

There are four naturally occurring isotopes of iron: ${ }_{26}^{54} Fe$, ${ }_{26}^{56}Fe$, ${ }_{26}^{57}Fe$, and ${ }_{26}^{58} Fe$ How many neutrons are in ${ }_{26}^{57} Fe$ ?

Below $912 ^ { \circ } \mathrm { C } ,$ pure iron crystallizes in a body-centered cubic structure (ferrite) with a density of 7.86 g/cm3; from $912 ^ { \circ } \mathrm { C }$ to $1394 ^ { \circ } \mathrm { C } ,$ it adopts a face-centered cubic structure (austenite) with a density of 7.40 g/cm3. Both types of iron form interstitial alloys with carbon. The maximum amount of carbon is 0.0218 mass% in ferrite and 2.08 mass% in austenite. Calculate the density of each alloy.

A student writes the equation below as the balanced equation for the reaction of iron with chlorine. Is this equation correct? Explain. $\mathrm{Fe}(s)+\mathrm{Cl}_{3}(g) \longrightarrow \mathrm{FeCl}_{3}(s)$

Determine the pressure drop per $100-\mathrm{m}$ length of horizontal new $0.20-\mathrm{m}$-diameter cast iron water pipe when the average velocity is $1.7 \mathrm{~m} / \mathrm{s}$.

A $1.2-\text{in}$-diameter bar of an iron-chromiumnickel alloy is to operate for 5 years under a load of $4000 \mathrm{lb}$. What is the maximum operating temperature? [See Figure 7-26(a).]

What is the pressure drop associated with water at $27^{\circ} \mathrm{C}$ flowing with a mean velocity of 0.2 m/s through a 600-m-long cast iron pipe of 0.15-m inside diameter?

The density of a substance is the ratio of its mass to its volume:

$$\text { Density }=\frac{\text { mass }}{\text { volume }} .$$

Density is usually expressed in terms of grams per cubic centimeter $\left(\mathrm{g} / \mathrm{cm}^3\right)$. For example, the density of copper is $8.94 \mathrm{~g} / \mathrm{cm}^3$

A piece of iron weighs $45$ ounces and has a volume of $10 \mathrm{in}^3$. Determine the density of iron in $\mathrm{g} / \mathrm{cm}^3$, rounding to the nearest tenth.

You are cooking breakfast for yourself and a friend using a 1 200-W waffle iron and a 500-W coffeepot. Usually, you operate these appliances from a 110-V outlet for 0.500 h each day. You find yourself addicted to waffles and would like to upgrade to a 2 400-W waffle iron that will enable you to cook twice as many waffles during a half-hour period, but you know that the circuit breaker in your kitchen is a 20-A breaker. Can you do the upgrade?

An iron-chromium-nickel alloy is to withstand a load of $1500 \mathrm{lb}$ at $760^{\circ} \mathrm{C}$ for 6 years. Calculate the minimum diameter of the bar. [See Figure 7-26(a).]

The galvanized iron pipe is used to carry water at $20^{\circ} \mathrm{C}$ with a velocity of $3 \mathrm{~m} / \mathrm{s}$. Find the pressure drop that occurs over a $4$-m length of the pipe.

How many kilojoules of heat will be released when exactly 1 mole of iron, Fe, is burned to form $\mathrm{Fe}_{2} \mathrm{O}_{3}(s)$ at standard state conditions?