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4 years ago

How many moles of gold atoms are in 2.8 x 10 21 atoms of gold?

Chemistry

2 answers:

8_murik_8 [283]4 years ago

6 0

Disregard the previous answer. You are not given anything in the way of grams, so you cannot assume the number of g from this. You would use Avogadro's Number, 6.02x10^23 in this case. I've attached a picture of how I found it. (Ignore my Statistics notes lol)

Westkost [7]4 years ago

4 0

Therefore, 1 mole of gold weighs 196.9665 grams. So, in 2.8 grams of gold we would have:
(2.8 gram)(1 mole/196.9665 gram) = 0.0142 mole.
From Avogadro's number, we know that there are approximately 6.02 x 1023atoms/mole.

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3 years ago

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A chemist dissolves 867. mg of pure barium hydroxide in enough water to make up 170. mL of solution. Calculate the pH of the sol

Ilya [14]

Answer: The pH of the solution is 11.2

Explanation:

Molarity of a solution is defined as the number of moles of solute dissolved per liter of the solution.

$Molarity=\frac{n\times 1000}{V_s}$

where,

n = moles of solute

$V_s$ = volume of solution in ml

moles of $Ba(OH)_2$ = $\frac{\text {given mass}}{\text {Molar mass}}=\frac{0.867g}{171g/mol}=0.00507mol$ (1g=1000mg)

Now put all the given values in the formula of molality, we get

$Molarity=\frac{0.00507\times 1000}{170}$

$Molarity=0.0298$

pH or pOH is the measure of acidity or alkalinity of a solution.

pH is calculated by taking negative logarithm of hydrogen ion concentration.

$pOH=-\log [OH^-]$

$Ba(OH)_2\rightarrow Ba^{2+}+2OH^{-}$

According to stoichiometry,

1 mole of $Ba(OH)_2$ gives 2 mole of $OH^-$

Thus 0.0298 moles of $Ba(OH)_2$ gives = $\frac{2}{1}\times 0.0298=0.0596$ moles of $OH^-$

Putting in the values:

$pOH=-\log[0.0596]=2.82$

$pH+pOH=14$

$pH=14-2.82$

$pH=11.2$

Thus the pH of the solution is 11.2

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Answer:

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In a 51.0-g aqueous solution of methanol ch4o the mole fraction of methanol is 0.270. what is the mass of each component?

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Mole fraction is another way of expressing the concentration of a solution or mixture. It is equal to the moles of one component divided by the total moles.

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Hope this answers the question. Have a nice day.

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