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Lesechka [4]
3 years ago
8

NEED HELP ASAPPP What is the number of beryllium atoms in 78.0g of Be?

Chemistry
1 answer:
polet [3.4K]3 years ago
4 0

Answer: number of atoms is 5.21 · 10^24

Explanation: Atomic mass of Be is 9.012 g/mol.

Number of moles n = m/M = 78.0 g / 9.012 g/mol =

Multiply this with Avogadro number Na = 6.022*10^23 1/mol

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In the drawing above, the hammer is acting as what type of simple machine? A. pulley B. screw C. wheel and axle D. lever
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The drawing above is acting as a B) a screw.

4 0
3 years ago
A reaction generates hydrogen gas (H) as a product. The re-
Amiraneli [1.4K]

<u>Answer:</u> The average rate of the reaction is 7.82\times 10^{-3}M/min

<u>Explanation:</u>

To calculate the molarity of hydrogen gas generated, we use the equation:

\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}

Moles of hydrogen gas = 3.91\times 10^{-2}mol

Volume of solution = 250 mL = 0.250 L    (Conversion factor: 1 L = 1000 mL)

Putting values in above equation, we get:

\text{Molarity of }H_2=\frac{3.91\times 10^{-2}mol}{0.250L}=0.1564M

Average rate of the reaction is defined as the ratio of concentration of hydrogen generated to the time taken.

To calculate the average rate of the reaction, we use the equation:

\text{Average rate of the reaction}=\frac{\text{Concentration of hydrogen generated}}{\text{Time taken}}

We are given:

Concentration of hydrogen generated = 0.1564 M

Time taken = 20.0 minutes

Putting values in above equation, we get:

\text{Average rate of the reaction}=\frac{0.1564M}{20.0min}\\\\\text{Average rate of the reaction}=7.82\times 10^{-3}M/min

Hence, the average rate of the reaction is 7.82\times 10^{-3}M/min

6 0
3 years ago
Suppose that a certain fortunate person has a net worth of $79.0 billion ($7.90×1010). If her stock has a good year and gains $3
mario62 [17]
A net worth: $79.0 billion.
Value of stock : $3.20 billion.
New net worth:
$79.0 + $3.20 = $82.20 billion = $82.20 * 10^9 = $8.20 * 10^10
7 0
3 years ago
Is the following a physical or chemical change?
tester [92]

Answer:

chemical change

Explanation:

electrolysis process by which electric current is passed through a substance to effect a chemical change.

6 0
2 years ago
A sample contains 16. 75 g of the radioisotope U-236 and 50. 25 g of its daughter isotope, Th-232. How long did it take for deca
garri49 [273]

The time taken for the isotope to decay is 46 million years.

We'll begin by calculating the number of half-lives that has elapsed. This can be obtained as follow:

  • Original amount (N₀) = 50.25 g
  • Amount remaining (N) = 16.75
  • Number of half-lives (n) =?

2ⁿ = N₀ / N

2ⁿ = N₀ / N

2ⁿ = 50.25 / 16.75

2ⁿ = 3

Take the log of both side

Log 2ⁿ = 3

nLog 2 = Log 3

Divide both side by log 2

n = Log 3 / Log 2

n = 2

Finally, we shall determine the time.

  • Half-life (t½) = 23 million years
  • Number of half-lives (n) = 2
  • Time (t) =?

t = n × t½

t = 2  × 23

t = 46 million years

Learn more about half-life: brainly.com/question/25927447

8 0
3 years ago
Read 2 more answers
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