1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
shtirl [24]
3 years ago
12

How many atoms are there in 90.2 grams of selenium?

Chemistry
1 answer:
Neko [114]3 years ago
4 0
First calculate the moles of selenium by multiplying the mass x molar mass
90.2 × 78.96 = 7122.2 moles

Number of moles multiplied by avogadros number gives number of atoms
7122.2 × 6.022 × 10^{23} = 4.289×10^{27} atoms
You might be interested in
Which of the following could be said about ecological footprints?
Thepotemich [5.8K]
<span>A. Exact ecological footprints are often difficult to calculate, but estimates can be useful in comparing populations.

</span>Which of the following could be said about ecological footprints? <u /> <u>Exact ecological footprints are often difficult to calculate, but estimates can be useful in comparing populations.</u><u />


NOT:
b. Ecological footprints can't be used to determine carrying capacity.
C. Ecological footprints don't take into account resources needed to absorb and manage wastes.
<span>D. The average ecological footprints for various countries are nearly identical.</span>
6 0
3 years ago
Would it be C???...idk<br> HELP
givi [52]

Answer:

C.  Butanal , is the aldehyde

Explanation:

A . It is carboxylic acid : ---COOH group

B. It is Ester : ----COOR group , Here R = CH3

C. It is Aldehyde : -----CHO group

D. It is ketone : ----C=O group

See image :

8 0
3 years ago
The goal of this lesson:
mote1985 [20]

Answer:

1. The concentration of N₂O₄ decrease as the temperature of the system increased.

2. The formation of products was favored by the addition of heat.

3. The reaction going from right to left is exothermic.

4. N₂O₄ → 2NO₂; HR = +14 kcal.

Explanation:

Equation of the reaction is as follows: N₂O₄ ⇄ 2NO₂

The forward reaction proceeds with an increase in temperature. As the temperature of the reaction was increased, more of the N₂O₄ decomposed to form NO₂. Therefore, the concentration of N₂O₄ deceased.

2. The formation of products, that is the forward reaction leading to formation of NO₂ was favored by the addition of heat. Thus, with increase in temperature, the concentration of NO₂ increased.

3. An endothermic reaction is a type of reaction which requires energy input in the form of heat in order to proceed.

From the observations during the reaction, an increase in temperature by the addition of heat resulted in an increase in the forward reaction, therefore, the forward reaction is endothermic and the backward reaction is exothermic. Thus, the reaction in which colorless N₂O₄ is produced, is an exothermic reaction.

4. The change in enthalpy of a reaction is the difference in the heat content of reactants and products. For exothermic reactions, enthalpy change is negative, whereas for endothermic reactions, enthalpy change is positive.

The decomposition of  N₂O₄ to NO₂ is an endothermic reaction. Hence, the correct chemical equation is: N₂O₄ → 2NO₂; HR = +14 kcal.

7 0
3 years ago
Stable nuclei with low atomic numbers, up to 20, have a neutron to proton ratio of approximately ________.
Pie
1 to 1. Most small atoms have the same number of protons and neutrons
6 0
3 years ago
An ionic bond can be formed when one or more electrons are 1) equally shared by two atoms 2) unequally shared by two atoms 3) tr
Lyrx [107]

Answer:

4) transferred from the valence shell of one atom to the valence shell of another atom

Explanation:

Electrons are located outside of the nucleus which contains the protons and the neutrons.

For bonds to form, valence electrons located in the outermost shell electrons are involved. These are the valence electrons. These outer shell electrons can be shared or transferred between two combining atoms to form stable atoms.

In ionic bonds, the electrons are transferred from one specie to another. The atom that loses the electrons becomes positively charged and the receiving atom becomes negatively charged. This is the crux of ionic bonds.

6 0
3 years ago
Other questions:
  • What are subscripts in a chemical formula and what do they stand for?
    6·2 answers
  • Which has a greater ionization energy, Ne or Gallium?
    6·1 answer
  • What does it mean for an element to be oxidized?
    7·1 answer
  • An HCl solution has a concentration of 0.09714 M. Then 10.00 mL of this solution was then diluted to 250.00 mL in a volumetric f
    14·1 answer
  • Which of the following is the largest volume?
    13·1 answer
  • Which statements are correct about Avogadro’s constant?
    13·1 answer
  • Electron configuration for iron?
    8·1 answer
  • WILL MARK BRAINLIST!!! only for correct answer<br> NEED CORRECT ANSWER ASAPPP
    9·1 answer
  • What is the purpose of continuing to heat a substance after it reaches a temperature plateau?
    5·1 answer
  • Which of the following are not made up of cells ( or a cell )
    5·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!