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3 years ago

How do I write 2.345 X 10^-4cm out of scientific notation?

Chemistry

1 answer:

alexira [117]3 years ago

6 0

0.0002345cm
when the power of the 10 is negative, it makes the number smaller

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The thermite reaction, in which powdered aluminum reacts with iron oxide, is highly exothermic: 2Al(s) + F e2O3 (s)→A l2O 3 (s)

bija089 [108]

For this problem, we use the Hess' Law.

ΔHrxn = ∑(ν*Hf of products) - ∑(ν*Hf of reactants)

The ν represents the corresponding stoichiometric coefficients of the substances, while Hf is the heat of formation. For pure elements, Hf = 0.

Hf of Al₂O₃ = −1676.4 kJ/mol
Hf of Fe₂O₃ = -826.0 kJ/mol

Thus,

ΔHrxn = 1*−1676.4 kJ/mol + 1*-826.0 kJ/mol
ΔHrxn = -2502.4 kJ/mol

4 0

3 years ago

What is the percentage yield of O2 if 12.3 g of KClO3 (molar mass 123 g) is decomposed to produce 3.2 g of O2 (molar mass 32 g)

My name is Ann [436]

Answer:

The percentage yield of O2 is 66.7%

Explanation:

Reaction for decomposition of potassium chlorate is:

2KClO₃ → 2KCl + 3O₂

The products are potassium chloride and oxygen.

Let's find out the moles of chlorate.

Mass / Molar mass = Moles

12.3 g / 123 g/mol = 0.1 mol

So ratio is 2:3, 2 moles of chlorate produce 3 mol of oxygen.

Then, 0.1 mol of chlorate may produce (0.1 .3)/ 2 = 0.15 moles

Let's convert the moles of produced oxygen, as to find out the theoretical yield.

0.15 mol . 32 g/ 1mol = 4.8 g

To calculate the percentage yield, the formula is

(Produced Yield / Theoretical yield) . 100 =

(3.2g / 4.8g) . 100 = 66.7 %

8 0

4 years ago

A 0.10 M aqueous solution of sodium sulfate, Na2SO4, is a better conductor of electricity than a 0.10 M aqueous solution of sodi

Dvinal [7]

Answer: D) More moles of ions are present in a given volume of 0.10 M $Na_2SO_4$ than in the same volume of 0.10 M NaCl.

Explanation:

A electrolyte is a solution that dissociates completely when dissolved in water. The ions act as good conductors of electric current in the solution.

More is the number of ions , more will be the conductance and hence the solution will be a better conductor of electricity.

0.10 M aqueous solution of $Na_2SO_4$ is a better conductor of electricity as it dissociates to give three ions whereas 0.10 M aqueous solution of $NaCl$ dissociates to give two ions only.

$Na_2SO_4\rightarrow 2Na^++SO_4^{2-}$

$NaCl\rightarrow Na^++Cl^{-}$

Thus 0.10 M aqueous solution of sodium sulfate, $Na_2SO_4$ , is a better conductor of electricity as more moles of ions are present in a given volume of 0.10 M $Na_2SO_4$ than in the same volume of 0.10 M $NaCl$

3 0

3 years ago

nikitadnepr [17]

Answer: The answer is B) 1.00 M CaCl2

Explanation: I just did it on usatestprep and it said it was correct .

8 0

3 years ago

Help please! Chem is not fun! :(

ad-work [718]

I think the answer is c

3 0

3 years ago