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3 years ago

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If thermal energy (heat) must be added to a chemical reaction in order for the reaction to take place, the reaction is _________

___.

1 answer:

Harlamova29_29 [7]3 years ago

7 0

<span>If thermal energy (heat) must be added to a chemical reaction in order for the reaction to take place, the reaction is endothermic. </span>

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Histamines are an important chemical in the body . what is their purpose in the immune system

pentagon [3]

Answer:

Histamine is a protein produced by <u>mast cells</u> in the body. It plays a very important role in the immune system of the body. Histamine is released in the body when <u>affected by an allergen</u>, e.g, pollen or animal dander. The immune system of the body will respond to such allergen by <u>making more mucus in the nose by releasing histamine</u>. There will be sneezing, itching, coughing and runny nose in response. This is a <u>basic defense of the body's immune system</u> to not enter any particle inside the body.

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3 years ago

Based on the name, which substance is a covalent compound?

Sindrei [870]

Answer:

dinitrogen pentoxide

Explanation:

Based on the research, dinitrogen pentoxide is a chemical compound containing only nitrogen and oxygen which is both nonmetal. When two nonmetals or two negatively charged atoms try to form bonds, they always form covalent bonds. Hence, Dinitrogen Pentoxide is not ionic - it is covalent.

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2 years ago

A sample of the mineral hematite Iron (III) oxide has a mass of 12.4g. How many moles of the mineral are present?

8090 [49]

Thus problem is providing us with the mass of iron (III) oxide as 12.4 g so the moles are required and found to be 0.0776 mol after the calculations:

<h3>Mole-mass relationships:</h3>

In chemistry, we use mole-mass relationships in order to calculate grams from moles and vice versa. In this case, since we are given the mass of iron (III) oxide as 12.4 g one can calculate the moles by firstly quantifying its molar mass:

$Fe_2O_3\rightarrow 2*55.85 g/mol+3*16.00 g/mol=159.7g/mol$

Then, we prepare a conversion factor in order to cancel out the grams and thus, get moles:

$12.4gFe_2O_3*\frac{1molFe_2O_3}{159.7gFe_2O_3} \\\\=0.0776molFe_2O_3$

Learn more about mole-mass relationships: brainly.com/question/18311376

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2 years ago

How many electrons in an atom can have each of the following quantum number or sublevel designations?

Karo-lina-s [1.5K]

Answer: (a) 2 (b) 6 (c) 14

Explanation:

In the Azimuthal quantum number(l) electrons in a particular subshell (such as s, p, d, or f) are defined by values of l (0, 1, 2, or 3).

s is l=0, p is l=1, d is l=2, f is l=3.

The magnetic quantum number (ml) The value of ml can range from -l to +l, including zero. Thus the s, p, d, and f subshells contain 1, 3, 5, and 7 orbitals each, with values of m within the ranges 0, ±1, ±2, ±3 respectively. Each shell can have 2 x l + 1 sublevels, and each of these sublevel can accommodate up to two electrons.

(a) n=2, l=1, ml=0. If l=1 then 2 x 1+ 1=3 sublevels, 3*2=6 electrons. When l=1, ml =-1,0,+1, ml=0 accommodate two(2)electrons

(b) 5p. p is l=1 If l=1 then 2 x 1+ 1=3 sublevels, 3*2= electrons. This means in the 5 shell, the p orbital has 3 subshell and accommodate 6 electrons.

(c) n = 4, l = 3 if l=3 then 2 x 3+ 1=7 sublevel 7*2=14 electrons. This means the in the 4 shell, the f orbital has 7 subshell and accomdate 14 elections.

7 0

2 years ago

64g of sulfur dioxide (SO2) contains 32g of oxygen. Calculate how much sulfur it contains?

KengaRu [80]

Mass of SO2 = mass of sulfur+ mass of oxygen
⇒ 64 g= mass of sulfur+ 32 g
⇒ mass of sulfur= 64 g-32 g
⇒ mass of sulfur= 32 g.

There is 32 g of sulfur in 64 g of SO2~

6 0

3 years ago