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3 years ago

How many atoms are in a sample of 68.7 g copper (Cu)?

2 answers:

8 0

Divide the number of grams present in the sample by copper's gram atomic weight to find the number of gram atomic weights present. Then multiply that result by Avogadro's Number: 6.022137 x 10^23 atoms/gram atomic weight.1,200 g/(63.54 g/gram atomic weight) ? 18.885741 gram-atomic weights. Hope this helps.

Helen [10]3 years ago

5 0

First convert grams into moles.
Then convert moles to atoms.

There are 63.546 grams of copper per mole. (This is just copper's atomic weight)
Thus, a 68.7 gram copper sample is (68.7/63.546) mols = 1.081 mols.

There are 6.022 * 10^23 atoms per mol.
6.022 * 10^23 * 1.081 = 6.52 * 10^23

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How many grams of H2O can be made from the combustion of 3.75 liters of C7H14 and an excess of O2 at STP?

Kitty [74]

Answer:

21.10g of H2O

Explanation:

We'll begin by writing the balanced equation for the reaction. This is given below:

2C7H14 + 21O2 —> 14CO2 + 14H2O

From the balanced equation above, 2L of C7H14 produced 14L of H2O.

Therefore, 3.75L of C7H14 will produce = (3.75 x 14)/2 = 26.25L of H2O.

Next, we shall determine the number of mole of H2O that will occupy 26.25L at stp. This is illustrated below:

1 mole of a gas occupy 22.4L at stp

Therefore, Xmol of H2O will occupy

26.25L i.e

Xmol of H2O = 26.25/22.4

Xmol of H2O = 1.172 mole

Therefore, 1.172 mole of H2O is produced from the reaction.

Next, we shall convert 1.172 mole of H2O to grams. This is illustrated below:

Number of mole H2O = 1.172 mole

Molar mass of H2O = (2x1) + 16 = 18g/mol

Mass of H2O =..?

Mass = mole x molar mass

Mass of H2O = 1.172 x 18

Mass of H2O = 21.10g

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3 years ago

Compound X has a molar mass of 266.64 g/mol and the following composition: aluminum 20.24% chlorine 79.76% Write the molecular f

N76 [4]

Answer:

Explanation:

Assume we have 100g of this substance. That means we would have 20.24g of Cl and 79.76g of Al. Now we can find how many moles of each we have:

$\frac{79.76 \:g}{35.45 \: g/mol}$ = 2.25 mol of chlorine

$\frac{20.24 \: g}{26.98 \: g/mol}$ = 0.750 mol of Al.

To form a integer ratio, do 2.25/0.75 = 2.99999 ~= 3.

So the ratio is essentially Al : Cl => 1 : 3. To the compound is possibly $AlCl_3$ .

However, it says it has a molar mass of 266.64 g/mol, and since AlCl3 has a molar mass of 133.32, it must be $Al_2Cl_6$ .

Actually this molecule isn't exactly AlCl3 (which is ionic). Al2Cl6 forms a banana bond where Cl acts as a hapto-2 ligand. But that's a bit advanced. All you need to know is X = Al2Cl6

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2 years ago

Using the systematic approach for equilibrium problems, calculate the pH of 0.05 M HOCl. Ka= 3.0*10-8 Group of answer choices 3.

SVEN [57.7K]

Answer:

The pH is equal to 4.41

Explanation:

Since HClO is a weak acid, its dissociation in aqueous medium is:

HClO ⇄ ClO- + H+

start: 0.05 0 0

change -x +x +x

balance 0.05-x x x