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3 years ago

How has the composition of the atmosphere changed overtime?

Chemistry

1 answer:

snow_lady [41]3 years ago

5 0

The composition of the atmosphere change over time by are humans activity

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Calculate the enthalpy change for the thermite reaction: 2Al(s)+Fe2O3(s)→2Fe(s)+Al2O3(s), ΔH∘rxn=−850 kJ when 12.0 mol of Al und

djverab [1.8K]

Answer: The enthalpy of the reaction for given amount of aluminium will be $-51.0\times 10^2kJ$

Explanation:

We are given:

Moles of aluminium = 12 moles

For the given chemical reaction:

$2Al(s)+Fe_2O_3(s)\rightarrow 2Fe(s)+Al_2O_3(s);\Delta H^o_{rxn}=-850kJ$

By Stoichiometry of the reaction:

If 2 moles of aluminium produces -850 kJ of energy.

Then, 12 moles of aluminium will produce = $\frac{-850kJ}{2mol}\times 12mol=-5100kJ$ of energy.

Converting this into three significant figures, we get:

$\Rightarrow -5100kJ=-51.0\times 10^{2}kJ$

Thus, the enthalpy of the reaction for given amount of aluminium will be $-51.0\times 10^2kJ$

4 0

3 years ago

A chemist used 6.5 moles of water in this reaction. How many grams of water were used?

denpristay [2]

Answer:

$\boxed {\boxed {\sf 120 \ or \ 117 \ grams \ H_2O \ depending \ on \ significant \ figures }}$

Explanation:

We want to convert from moles of water to grams of water.

First, find the molar mass of water (H₂O) Look on the Periodic Table for the masses of hydrogen and oxygen.

Hydrogen (H): 1.008 g/mol
Oxygen (O): 15.999 g/mol

Next, add up the number of each element in water. The subscript of 2 comes after the H, so there are 2 moles of hydrogen.

2 Hydrogen: (1.008 g/mol*2) = 2.016 g/mol

Finally, add the molar mass of 2 hydrogen and 1 oxygen.

2.016 g/mol (2 Hydrogen) + 15.999 g/mol (1 oxygen)= 18.015 g/mol

Next, find the grams in 6.5 moles.

Use the molar mass we just found as a ratio.

$molar \ mass \ ratio: \frac{18.015 \ g \ H_2O}{1 \ mol \ H_2O}$

We want to find the grams in 6.5 moles. We can multiply the ratio above by 6.5

$6.5 \ mol \ H_2O * \frac{18.015 \ g \ H_2O}{1 \ mol \ H_2O}$

Multiply. Note that the moles of H₂O will cancel each other out.

$6.5 * \frac{18.015 \ g \ H_2O}{1}$

$6.5 * {18.015 \ g \ H_2O}$

$117.0975 \ g \ H_2O$

If we want to round to the technically correct significant figures, it would be 2 sig figs. The original measurement, 6.5, has 2 (6 and 5).

$\approx 120 \ g \ H_2O$

6 0

3 years ago

Can someone plz help me?? The question is in the pic...TYSM!!

Mnenie [13.5K]

Answer:

3 is the correct answer i think

Explanation:

4 0

3 years ago

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Hellllllppppppp!!!!!!!! 5 more minnnnnnn C. To produce D. To have a purpose

riadik2000 [5.3K]

I believe it is C) to produce

6 0

3 years ago

What does Nb stand for on the periodic table? Pls help! Need aware soon

Marina86 [1]

It stands for niobium which was discovered in 1801 by Charles Hatchett of Brittan. It is ussed in welding rods, air fraim systems, superconductive magnets. It gets its name from iobe, the daughter of King Tantalus of the Greek myth. Niobium was considered identical to Tantalum, named after Tantalus, until 1884. Resists corrosin due to an oxide film. It is used in aviation industry

4 0

3 years ago

Read 2 more answers