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Irina-Kira [14]
3 years ago
9

If you examined the human body on a chemical composition basis, which of the following combinations of elements would be most co

mmon?? (A) C, H, Ca, Cl (B) O, C, P, S (C) O, C, H, N (D) O, C, N, Na (E) C, N, Ca, S
Chemistry
1 answer:
Harlamova29_29 [7]3 years ago
5 0

Answer:

(C) O, C, H, N

Explanation:

<u>Roughly 96% of mass of human body is made up of four elements which are oxygen, carbon, nitrogen and hydrogen.</u>

Oxygen and hydrogen are predominantly found in the water, which makes up about 60% of body's weight. Carbon is synonymous with the life. The central role of carbon is due to fact that it has four bonding sites which allow for building of long and complex chains of the molecules. Moreover, these carbon bonds can be formed and also be broken with amount of energy which makes life alive. Nitrogen is found in organic molecules, including amino acids which make up the proteins, and nucleic acids which make up the DNA.

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Calculate δ h for the reaction:no (g) + o2 (g) ↔ no2 (g). given: 2o3(g) ↔ 3o2(g) δh=-426 kj o2(g) ↔ 2o(g) δh=+ 490 kj no(g) + o3
maks197457 [2]
To calculate the <span>δ h, we must balance first the reaction: 

NO + 0.5O2 -----> NO2

Then we write all the reactions,

2O3 -----> 3O2    </span><span>δ h = -426 kj        eq. (1)

O2 -----> 2O    </span><span>δ h = 490 kj             eq. (2)

NO + O3 -----> NO2 + O2    </span><span>δ h = -200 kj          eq. (3)


We divide eq. (1) by 2, we get

</span>O3 -----> 1.5O2    δ h = -213  kj             eq. (4)

Then, we subtract eq. (3) by eq. (4) 

NO + O3 ----->  NO2 + O2   δ h = -200 kj
-       (O3 -----> 1.5 O2         δ h = -213  kj)
NO -----> NO2 - 0.5O2        δ h = 13  kj               eq. (5)


eq. (2) divided by -2. (Note: Dividing or multiplying by negative number reverses the reaction)

O -----> 0.5O2  <span>δ h = -245  kj         eq. (6)
</span>
Add eq. (6) to eq. (5), we get

NO -----> NO2 - 0.5O2        δ h = 13  kj 
+  O -----> 0.5O2                 δ h = -245  kj
NO + O ----> NO2               δ h = -232 kj

<em>ANSWER:</em> <em>NO + O ----> NO2               δ h = -232 kj</em>


4 0
3 years ago
P4O10 -&gt; 4P+5O2 How many moles of phosphorus would be produced if 5.3 mol of P4O10 reacted?
viktelen [127]

Answer:

21.2 moles.

Explanation:

Hello!

In this case, for the given chemical reaction, we can see there is a 1:4 mole ratio between tetraphosphorous decaoxide and phosphorous; therefore, the following proportional factor provides the requested moles of phodphorous:

n_P=5.3molP_4O_{10} *\frac{4molP}{1molP_4O_{10}} \\\\n_P=21.2molP

Best regards!

5 0
3 years ago
2. A student has a centrifuge tube containing 14.0 g of t-butanol and is asked to make a 1.2 m solution of ethanol/t-butanol. Ho
Vaselesa [24]

Answer:

0.774g of ethanol

0.970mL of ethanol

Explanation:

Molality is an unit of concentration defined as the ratio between moles of solute and kg of solvent.

In the problem, you need to prepare a 1.2m solution of ethanol (Solute) in t-butanol (solvent).

14.0g of butanol are <em>0.014kg </em>and as you want to prepare the 1.2m solution, you need to add:

0.014kg × (1.2moles / kg) = 0.0168 moles of solute = Moles of ethanol

To convert moles of ethanol to mass you require molar mass (Molar mass ethanol, C₂H₅OH = 46.07g/mol). Thus, mass of 0.0168 moles are:

0.0168moles Ethanol ₓ (46.07g / mol) =

<h3>0.774g of ethanol</h3>

And to convert mass in g to mL you require density of the substance (Density of ethanol = 0.798g/mL):

0.774g ₓ (1mL / 0.798g) =

<h3>0.970mL of ehtanol</h3>
8 0
3 years ago
How many isomeric esters including structural isomers and stereoisomers can be made with the molecular formula C5H10O2 if methan
defon
Methanoic acid has a molecular formula of HCOOH, when form an ester it's HCOO-, so the rest of the ester is -C4H9, a saturated 4 carbon chain.  As shown in the attached diagram, there are 4 structural isomers, and the third isomer has 2 stereoisomers. So the answers is D:5.

3 0
3 years ago
Write the atomic symbols for isotopes with the following characteristics? 1)an oxygen atom with 10 neutrons 2)a neon atom with t
VARVARA [1.3K]
Isotopes are elements that differ in the number in neutrons while the numner of protons are the same. The answers of the questions are: 1) 18/8 O 2) 22/10 Ne 3) 53/25 Mn 4) 37/24 Cr 5) 106/81 Ti.
8 0
3 years ago
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