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Elanso [62]
3 years ago
15

A mover packs books, CDs, and DVDs into a moving box. If the box contains 6.5 kg of books, 1.5 kg of CDs, and 2.0 kg of DVDs, wh

at is the percent by mass of each object in the box?
Chemistry
2 answers:
IrinaVladis [17]3 years ago
7 0

Answer:

\text{Mass percentage}=\frac{\text{Mass of the substance}}{\text{Total mass}}\times 100

Given: Mass of books = 6.5 kg

Mass of CD's = 1.5 kg

Mass of DVD's = 2.0 kg

Total mass = 6.5 kg + 1.5 kg + 2.0 kg = 10 kg

\text {Mass percentage of books}=\frac{6.5kg}{10kg}\times {100}=65\%

\text {Mass percentage of CD's}=\frac{1.5kg}{10kg}\times {100}=15\%

\text {Mass percentage of DVD's}=\frac{2.0kg}{10}\times {100}=20\%

andrezito [222]3 years ago
4 0
<span>First, we calculate the total mass.

M = 6.5 kg + 1.5 kg + 2.0 kg =  10 kg

Percent by mass is calculated by getting the ration of the mass of an object and the total mass multiplied by 100 to get the percent.

%M1 = 6.5 / 10 x 100 = 65%
%M2 = 1.5/10 x 100 = 15%
<span>%M3 = 2.0/10 x 100 = 20%</span></span>
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  • Question 19: the three are molecular compounds.
  • Question 20: CuSO₄.5H₂O

Explanation:

<em>Question 19.</em>

  • C₂H₄
  • HF
  • H₂O₂

All of them are the combination of two kinds of different atoms in fixed proportions.

  • C₂H₄: two carbon atoms per four hydrogen atoms
  • HF: one hydrogen atom per one fluorine atom
  • H₂O₂: two hydrogen atoms per two oxygent atoms

Thus, they all meet the definition of compund: a pure substance formed by  two or more different elements with a definite composition.

Molecular compounds are formed by covalent bonds and ionic compounds are formed by ionic bonds.

Two non-metal elements, like H-F, C - C, C - H, H-O, H - H, and O - O will share electrons forming covalent bonds to complete their valence shell. Thus, the three compounds are molecular and not ionic.

<em>Question 20. </em>Formula of copper(II) sulfate hydrate with 36.0% water.

Copper(II) sulfate is CuSO₄. Its molar mass is 159.609g/mol

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Calling x the number of water molecules in the hydrate, the percentage of water is:

       \dfrac{18.015x}{18.015x+159.609}=36\%\\ \\ \\ \dfrac{18.015x}{18.015x+159.609}=0.36

From which we can solve for x:

      18.015x=6.4854x+57.45924\\ \\ 11.5296x=57.45924\\ \\ x\approx4.98\approx5

Thus, there are 5 molecules of water per each unit of CuSO₄, and the formula is:

  • CuSO₄.5H₂O
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