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3 years ago

I'm very confused please help

Chemistry

1 answer:

Setler79 [48]3 years ago

5 0

Answer:

the food chain you mean

Explanation:

pollution than mosquitoes then alligators

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3 years ago

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17. What is the symbol for the element that forms a.

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3 years ago

A copper wire is 44.85 cm long and weighs 1.521 g. The density of copper is 8.933 g/cm3.

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3 years ago

Find the number of moles in 1.00 x 1023 atoms of chromium.

IRISSAK [1]

Answer:

<h2>0.17 moles</h2>

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

$n = \frac{N}{L} \\$

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

We have

$n = \frac{1.00 \times {10}^{23} }{6.02 \times {10}^{23} } = \frac{1}{6.02} \\ = 0.166112$

We have the final answer as

<h3>0.17 moles</h3>

Hope this helps you

8 0

3 years ago

How many grams of sodium fluoride should be added to 300. mL of 0.0310 M of hydrofluoric acid to produce a buffer solution with

Kisachek [45]

Answer : The mass of sodium fluoride added should be 0.105 grams.

Explanation : Given,

The dissociation constant for HF = $K_a=6.8\times 10^{-4}$

Concentration of HF (weak acid)= 0.0310 M

First we have to calculate the value of $pK_a$ .

The expression used for the calculation of $pK_a$ is,

$pK_a=-\log (K_a)$

Now put the value of $K_a$ in this expression, we get:

$pK_a=-\log (6.8\times 10^{-4})$

$pK_a=4-\log (6.8)$

$pK_a=3.17$

Now we have to calculate the concentration of NaF.

Using Henderson Hesselbach equation :

$pH=pK_a+\log \frac{[Salt]}{[Acid]}$

$pH=pK_a+\log \frac{[NaF]}{[HF]}$

Now put all the given values in this expression, we get:

$2.60=3.17+\log (\frac{[NaF]}{0.0310})$

$[NaF]=0.00834M$

Now we have to calculate the moles of NaF.

$\text{Moles of NaF}=\text{Concentration of NaF}\times \text{Volume of solution}=0.00834M\times 0.300L=0.0025mole$

Now we have to calculate the mass of NaF.

$\text{Mass of }NaF=\text{Moles of }NaF\times \text{Molar mass of }NaF=0.0025mole\times 42g/mole=0.105g$

Therefore, the mass of sodium fluoride added should be 0.105 grams.

4 0

4 years ago

I'm very confused please help​

I'm very confused please help