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choli [55]
3 years ago
13

How are atoms and elements alike and different?

Chemistry
1 answer:
Vika [28.1K]3 years ago
8 0
An element is an atom or group of the same type of atom in a concentrated, pure form. A molecule is a group of atoms that aren't all necessarily the same type of element. For example, in a sample of elemental iron, every atom in the sample will be an iron atom whereas in table salt, NaCl, half of the atoms are sodium atoms and the rest are chlorine atoms. Atoms are composed of a nucleus which has neutrally charged neutrons and  positively charged protons, surrounded by a cloud of negatively charged electrons. Number of electrons and neutrons may vary from atom to atom of the same element, but the number of protons in the atom determine what element it is.
 
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g When 2.50 g of methane (CH4) burns in oxygen, 125 kJ of heat is produced. What is the enthalpy of combustion (in kJ) per mole
Anna [14]

Answer:

-800 kJ/mol

Explanation:

To solve the problem, we have to express the enthalpy of combustion (ΔHc) in kJ per mole (kJ/mol).

First, we have to calculate the moles of methane (CH₄) there are in 2.50 g of substance. For this, we divide the mass into the molecular weight Mw) of CH₄:

Mw(CH₄) = 12 g/mol C + (1 g/mol H x 4) = 16 g/mol

moles CH₄ = mass CH₄/Mw(CH₄)= 2.50 g/(16 g/mol) = 0.15625 mol CH₄

Now, we divide the heat released into the moles of CH₄ to obtain the enthalpy per mole of CH₄:

ΔHc = heat/mol CH₄ = 125 kJ/(0.15625 mol) = 800 kJ/mol

Therefore, the enthalpy of combustion of methane is -800 kJ/mol (the minus sign indicated that the heat is released).

3 0
2 years ago
How many atoms are there in 7.80 moles of germanium
Orlov [11]
<h3>Answer:</h3>

4.70 × 10²⁴ atoms Ge

<h3>General Formulas and Concepts:</h3>

<u>Math</u>

<u>Pre-Algebra</u>

Order of Operations: BPEMDAS

  1. Brackets
  2. Parenthesis
  3. Exponents
  4. Multiplication
  5. Division
  6. Addition
  7. Subtraction
  • Left to Right

<u>Chemistry</u>

<u>Atomic Structure</u>

  • Using Dimensional Analysis
  • Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.
<h3>Explanation:</h3>

<u>Step 1: Define</u>

7.80 mol Ge

<u>Step 2: Identify Conversions</u>

Avogadro's Number

<u>Step 3: Convert</u>

\displaystyle 7.80 \ mol \ Ge(\frac{6.022 \cdot 10^{23} \ atoms \ Ge}{1 \ mol \ Ge} ) = 4.69716 × 10²⁴ atoms Ge

<u>Step 4: Check</u>

<em>We are given 3 sig figs. Follow sig fig rules and round.</em>

4.69716 × 10²⁴ atoms Ge ≈ 4.70 × 10²⁴ atoms Ge

8 0
2 years ago
What is the percent by volume of ethanol (C2H60, or ethyl alcohol) in the final solution when 90 mL of ethanol is diluted to a v
r-ruslan [8.4K]

Answer:

16.0%.

Explanation:

Volume percent of a substance is the ratio of the substance volume to the solution volume multiplied by 100.

V % of ethanol = (volume of ethanol / volume of the solution) x 100.

volume of ethanol = 90.0 mL, volume of the solution = 550.0 mL.

∴ V % of ethanol = (90.0 mL / 550.0 mL) x 100 = 16.36% ≅ 16.0%.

8 0
2 years ago
"What volume of" a 0.300 M BaF2 "solution is needed to prepare" 240.0 mL of a 0.100 M F- solution
zhannawk [14.2K]
Use M x V = M' x V'

0.300 x V = 0.100 x 250

V = .......... ml
6 0
3 years ago
What is the electron configuration of the calcium ion?​
Elanso [62]
[Ar] 4s²
Let me know if you want a step by step!
Hope that helps
4 0
3 years ago
Read 2 more answers
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