Course: 12.4 质量质量计量法

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质量- mass 口道测量法
How many walnuts are needed to equal 250 grams?
::需要多少核桃才能等于250克?

I want to send 250 grams of shelled walnuts to a friend (don’t ask why – just go with the question). How many walnuts in shells do I need to buy? To figure this out, I need to know how much the shell of a walnut weighs (about 40% of the total weight of the unshelled walnut). I can then calculate the mass of walnuts that will give me 250 grams of shelled walnuts and then determine how many walnuts I need to buy.
::我想把250克贝壳核桃寄给一位朋友(不要问为什么 — — 只要回答一个问题就可以了 ) 。我要买多少贝壳核桃? 要搞清楚这一点,我需要知道核桃壳的重量(约为未壳核桃总重量的40% ) 。然后我就可以计算出核桃的重量,这些核桃将给我250克贝壳核桃,然后确定我需要买多少核桃。

Mass to Mass Problems
::大众至大众问题

Mass-mass calculations are the most practical of all mass-based stoichiometry problems. Moles cannot be measured directly, while the mass of any substance can generally be easily measured in the lab. This type of problem is three steps and is a combination of the two previous types.
::质量量量计算是所有基于质量的声学测量问题中最实际的问题。摩尔无法直接测量, 而任何物质的质量一般都可以在实验室中轻易测量。这类问题分为三个步骤,是前两种类型的结合。

$\begin{aligned} mass of g i v e n \to moles of g i v e n \to moles of u n k n o w n \to mass of u n k n o w n \end{aligned}$
$\begin{align*}\text{mass of} \ given \rightarrow \text{moles of} \ given \rightarrow \text{moles of} \ unknown \rightarrow \text{mass of} \ unknown\end{align*}$
::未知未知的未知质量

The mass of the given substance is converted into moles by use of the of that substance from the periodic table . Then, the moles of the given substance are converted into moles of the unknown by using the from the balanced chemical equation . Finally, the moles of the unknown are converted to mass by use of its molar mass.
::特定物质的质量通过使用周期表中的该物质而转换成摩尔。然后,特定物质的摩尔通过使用平衡化学方程的摩尔转化为未知物的摩尔。最后,未知物的摩尔通过使用其摩尔质量而转换成质量。

Sample Problem: Mass-Mass Stoichiometry
::样本问题: 质量- mass 口测量法

Ammonium nitrate decomposes to dinitrogen monoxide and water according to the following equation.
::硝酸铵按照以下公式分解为一氧化二氮和水。

$\begin{aligned} {NH}_{4} {NO}_{3} (s) \to N_{2} O (g) + 2 H_{2} O (l) \end{aligned}$
$\begin{align*}\text{NH}_4\text{NO}_3 (s) \rightarrow \text{N}_2 \text{O}(g)+2\text{H}_2\text{O}(l)\end{align*}$
::NH4NO3 +N2O(g)+2H2O(l)

In a certain , 45.7 g of ammonium nitrate is decomposed. Find the mass of each of the products formed.
::在一定量的45.7克硝酸铵中,将分解为45.7克硝酸铵。

Step 1: List the known quantities and plan the problem.
::第1步:列出已知数量并规划问题。

Known
::已知已知

given: 45.7 g NH ₄ NO ₃
::说明:45.7克NH4NO3

1 mol NH ₄ NO ₃ = 1 mol N ₂ O = 2 mol H ₂ O (mole ratios)
::1 mol NH4NO3 = 1 mol N2O = 2 mol H2O (死亡率)

molar mass of NH ₄ NO ₃ = 80.06 g/mol
::NH4NO3 = 80.06克/摩尔

molar mass of N ₂ O = 44.02 g/mol
::N2O = 44.02 克/摩尔的摩尔摩尔质量

molar mass of H ₂ O = 18.02 g/mol
::H2O = 18.02 克/摩尔的摩拉质量

Unknown
::未知

mass N ₂ O = ? g
::质量N2O=? g

mass H ₂ O = ? g
::质量 H2O =? g

Perform two separate three-step mass-mass calculations as shown below.
::执行如下所示的两步三步质量计算。

$\begin{aligned} {g NH}_{4} {NO}_{3} \to {mol NH}_{4} {NO}_{3} \to {mol N}_{2} O \to {g N}_{2} O \\ {g NH}_{4} {NO}_{3} \to {mol NH}_{4} {NO}_{3} \to {mol H}_{2} O \to {g H}_{2} O \end{aligned}$
$\begin{align*}& \text{g NH}_4\text{NO}_3 \rightarrow \text{mol NH}_4\text{NO}_3 \rightarrow \text{mol N}_2\text{O} \rightarrow \text{g N}_2\text{O}\\ & \text{g NH}_4\text{NO}_3 \rightarrow \text{mol NH}_4\text{NO}_3 \rightarrow \text{mol H}_2\text{O} \rightarrow \text{g H}_2\text{O}\end{align*}$
::g NH4NO3NH4NO3Mol NH4NO3Mol N2Og N2Og N2Og NH4NO3Mol NH4NO3NH4NO3Mol H2Og H2OOO

Step 2: Solve.
::步骤2:解决。

$\begin{aligned} 45.7 {g NH}_{4} {NO}_{3} \times \frac{1 {mol NH}_{4} {NO}_{3}}{80.06 {g NH}_{4} {NO}_{3}} \times \frac{1 {mol N}_{2} O}{1 {mol NH}_{4} {NO}_{3}} \times \frac{44.02 {g N}_{2} O}{1 {mol N}_{2} O} = 25.1 {g N}_{2} O \\ 45.7 {g NH}_{4} {NO}_{3} \times \frac{1 {mol NH}_{4} {NO}_{3}}{80.06 {g NH}_{4} {NO}_{3}} \times \frac{2 {mol H}_{2} O}{1 {mol NH}_{4} {NO}_{3}} \times \frac{18.02 {g H}_{2} O}{1 {mol H}_{2} O} = 20.6 {g H}_{2} O \end{aligned}$
$\begin{align*}& 45.7 \text{ g NH}_4\text{NO}_3 \times \frac{1 \text{ mol NH}_4\text{NO}_3}{80.06 \text{ g NH}_4\text{NO}_3} \times \frac{1 \text{ mol N}_2 \text{O}}{1 \text{ mol NH}_4\text{NO}_3} \times \frac{44.02 \text{ g N}_2\text{O}}{1 \text{ mol N}_2\text{O}}=25.1 \text{ g N}_2\text{O}\\ & 45.7 \text{ g NH}_4\text{NO}_3 \times \frac{1 \text{ mol NH}_4\text{NO}_3}{80.06 \text{ g NH}_4 \ \text{NO}_3} \times \frac{2 \text{ mol H}_2\text{O}}{1 \text{ mol NH}_4\text{NO}_3} \times \frac{18.02 \text{ g H}_2\text{O}}{1 \text{ mol H}_2\text{O}}=20.6 \text{ g H}_2\text{O}\end{align*}$
::45.7 g NH4NO3×1 mol NH4NO3×1 mol NH4NO3.80.06 g NH4NO3×1 mol N2O1 mol N2O1 mol NH4NO3×44.02 g N2O1 mol N2O1 mol N2O=25.1 g N2O45.7 g N2O45.7 g NH4NO3×1 mol NH4NO3.80.06 g NH4 NO3×2 mol H2O1 mol H2O1 mol NH4NO3×18.02 g H2O1 mol H2O=20.6 g H2O

Step 3: Think about your result.
::步骤3:想想你的结果。

The total mass of the two products is equal to the mass of ammonium nitrate which decomposed, demonstrating the . Each answer has three .
::这两种产品的总质量等于硝酸铵的重量,硝酸铵分解,以证明:每个回答有三个。

Summary
::摘要

Mass-mass calculations involve converting the mass of a reactant to moles of reactant, then using mole ratios to determine moles of product which can then be converted to mass of product.
::质量计算涉及将反应剂的质量转换为反应剂的摩尔,然后使用摩尔比率确定产品中的摩尔,然后可以转换成产品质量。

Review
::回顾

If matter is neither created nor destroyed, why can’t we just go directly from grams of reactant to grams of product?
::如果物质既非创造也非毁灭, 为什么我们不能直接从反应剂克直接变成产品克?

Why is it important to get the subscripts correct in the formulas?
::为什么必须在公式中纠正下标?

Why do the coefficients need to be correct?
::为什么系数必须正确?

Section outline

General

质量- mass 口道测量法

How many walnuts are needed to equal 250 grams? ::需要多少核桃才能等于250克?

Mass to Mass Problems ::大众至大众问题

Sample Problem: Mass-Mass Stoichiometry ::样本问题: 质量- mass 口测量法

Summary ::摘要

Review ::回顾

How many walnuts are needed to equal 250 grams?
::需要多少核桃才能等于250克?

Mass to Mass Problems
::大众至大众问题

Sample Problem: Mass-Mass Stoichiometry
::样本问题: 质量- mass 口测量法

Summary
::摘要

Review
::回顾