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2 years ago

3.

Chemistry

1 answer:

Vsevolod [243]2 years ago

3 0

Answer:

2 half-lives=0.8

6 half-lives= 0.05

Explanation

Half-lives are constant and always decrease by half, implying that the concentration decreases by half at a consistent rate.

3.2/2= 1.6/2= 0.8 is two half-lives

3.2/2= 1.6/2= 0.8/2= 0.4/2= 0.2/2= 0.1/2=0.05 is six half-lives

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shtirl [24]

Answer: D) 1.00 g

Explanation:

According to the Avogadro's law, the volume of gas is directly proportional to the number of moles of gas at same pressure and temperature. That means,

$V\propto n$

or,

$\frac{V_1}{V_2}=\frac{n_1}{n_2}$

where,

$V_1$ = initial volume of gas = 2.00 L

$V_2$ = final volume of gas = 3.00 L

$n_1$ = initial moles of gas = $\frac{\text {Given mass of helium}}{\text {molar mass of helium}}=\frac{2.00g}{4g/mol}=0.500mol$

$n_2$ = final moles of gas = ?

Now we put all the given values in this formula, we get

$\frac{2.00L}{3.00L}=\frac{0.500mol}{n_2}$

$n_2=0.75mole$

Mass of helium = $moles\times {\text {molar mass}}=0.75\times 4=3.00g$

Thus mass of helium added = (3.00-2.00) g = 1.00 g

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3 years ago

How can we prevent rusting of iron??

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3 years ago

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2 years ago

Which of the following ions is formed when a base is dissolved in a solution?

Aneli [31]

Answer:

$\huge\boxed{\sf OH-}$

Explanation:

<u>According to Arrhenius concept of acid and base:</u>

"When a base in a solution, produces/yields OH- (Hydroxide) ions."

So, when a base is dissolved in a solution, it produces OH- ions.

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$\rule[225]{225}{2}$

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2 years ago

How many moles are represented by 3.01x10^23 helium atoms

Alex787 [66]

Answer:

b. 0.50 moles

Explanation:

To solve this problem we use <em>Avogadro's number</em> (6.023x10²³ atoms/mol).

By <u>dividing the number of atoms (or molecules) by that number</u>, we can calculate how many moles they represent.

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