In determining the mass percent in CH2O. We have to multiply the molar mass of hydrogen by 2 because:

Question

BlackTom AI · Accepted Answer

When evaluating why we multiply the hydrogen mass by 2 in CH2O, we start by identifying what the molecule actually contains.
Option 1: "because there is a carbon and an oxygen" — This is not the reason. The presence of C and O does not dictate multiplying H by 2; mass percent depends on the number of hydrogen atoms, not on which other elements are present.
Option 2: "because you always multiply hydrogen's mass by 2" — This is a generalization that isn’t true. We do not multiply hydrogen by 2 in all compounds; we multiply by 2 only when there are two hydrogen atoms in the specific formula unit, as with CH2O.
Option 3: "there are two hydrogens" — This is correct. CH2O contains two hydrogen atoms, so the total mass contributed by hydrogen is 2 × (mass of one H). This directly affects the hydrogen portion of the molar mass and thus the mass percent of hydrogen in the compound.
Putting it together, to compute mass percent of H in CH2O you take 2 × (molar mass of H) divided by the molar mass of CH2O and multiply by 100%. The key point is counting how many hydrogen atoms are present, not applying a blanket rule or the presence of other elements.
In summary, option 3 correctly identifies the reason—the molecule has two hydrogen atoms—while options 1 and 2 rely on incorrect justifications or overgeneralizations that do not apply here.

1A W25 Emperical and Molecular formulas and Mass Percent and Molecular Composition (3 videos)

In determining the mass percent in CH2O. We have to multiply the molar mass of hydrogen by 2 because:

查看解析

登录即可查看完整答案

类似问题

What is the percent composition by mass of carbon in a sample of propanol, CH3CH2CH2OH? The molar mass of propanol is 60.09 g∙mol–1.

Ibuprofen is an anti-inflammatory drug that is used to treat pain, fever, and inflammation. It's molecular formula is C13H18O2. What is the mass percent of C in ibuprofen?

If a sample of C4H8O3 is found to contain 3.89 g of C atoms, how many grams of O atoms are present in the sample?

What is the percentage composition by mass of sulfur in silver thiosulfate (Ag2S2O3)?

The mass of silver in 9.000 g of silver chloride, AgCl(s), is:

The % oxygen by mass of a Group 2 oxide is 39.7%. Name the Group 2 element.

What is the percent by weight of Cl in DDT, C14H9Cl5?

Which of the following has the largest percentage of carbon in the compound?

更多留学生实用工具

考试浏览器助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单