Question

How many formula units are in 0.335 g CaO?

Answer 1

The empirical formula of any ionic or covalent network solid molecule utilised as a separate entity for stoichiometric calculations is known as a formula unit. We use this concept here. The conversion factor is found out from the question to find the answer.

Complete answer:
Calcium oxide, often known as quicklime or burned lime, is a chemical substance that is frequently used. At room temperature, it is a white, caustic, alkaline, crystalline solid. The word "lime" refers to calcium-containing inorganic compounds that are mostly composed of carbonates, oxides, and hydroxides of calcium, silicon, magnesium, aluminium, and iron. Quicklime, on the other hand, refers to the single chemical molecule calcium oxide.
Let's try to come up with a conversion factor that will take us straight from the number of grams of calcium oxide in the sample to the number of formula units. Look up the molar mass of calcium oxide to begin. ${{M}_{M}}\text{ }CaO=56.0774\text{ }g\text{ }mo{{l}^{-1}}$ M
This indicates that 1 mole of calcium oxide weighs 56.0774 g, which may be expressed as a conversion factor. $\dfrac{1\text{ }mole\text{ }CaO}{56.0774\text{ }g}$
You now know that $6.022\times {{10}^{23}}$ formula units of calcium oxide are required to make 1 mole of calcium oxide. Avogadro's constant is what it's called.
This can also be expressed as a conversion factor which is $\dfrac{\text{1 mole CaO}}{\text{6}\text{.022 }\\!\\!\times\\!\\!\text{ 1}{{\text{0}}^{\text{23}}}\text{.formula units}}$
The two conversion factors, as you can see, share a quantity. If you add these two conversion factors together, you get
$\dfrac{\text{1 mole CaO}}{\text{56}\text{.0774 g}}\text{ }\\!\\!\times\\!\\!\text{ }\dfrac{\text{6}\text{.022 }\\!\\!\times\\!\\!\text{ 1}{{\text{0}}^{\text{23}}}\text{.formula units}}{\text{1 mole CaO}}$
You'll get it as
$\dfrac{\text{6}\text{.022 }\\!\\!\times\\!\\!\text{ 1}{{\text{0}}^{\text{23}}}\text{.formula units}}{\text{56}\text{.0774 g}}$
You now have a conversion factor that allows you to go from grams to formula units and back. So you've determined that your sample weighs 0.335 g. To get, multiply this by the conversion factor.
$\text{0}\text{.335g }\\!\\!\times\\!\\!\text{ }\dfrac{\text{6}\text{.022 }\\!\\!\times\\!\\!\text{ 1}{{\text{0}}^{\text{23}}}\text{ formula units}}{\text{56}\text{.0774g}}$
$\Rightarrow \text{3}\text{.60 }\\!\\!\times\\!\\!\text{ 1}{{\text{0}}^{\text{21}}}\text{.formula units}$
The answer is rounded to three sig figs since you have three sig figs for the mass of calcium oxide.

Note:
Limestone can be used in place of lime in a variety of applications, including agriculture, fluxing, and sulphur removal. Limestone, which contains less reactive material, reacts more slowly and may have additional drawbacks in comparison to lime, depending on the application; nevertheless, limestone is significantly less costly than lime. Calcined gypsum is used in industrial plasters and mortars as a substitute for natural gypsum. Some building applications of lime can be replaced by cement, cement kiln dust, fly ash, and lime kiln dust.