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Cerrena [4.2K]
3 years ago
15

Which two observations below can be evidence that a chemical change has occurred

Chemistry
1 answer:
larisa86 [58]3 years ago
5 0
Vaporization and Production of bubbles. Production of heat and melting are physical changes
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Complete combustion of 7.40 g of a hydrocarbon produced 22.4 g of CO2 and 11.5 g of H2O. What is the empirical formula for the h
cluponka [151]
<span>C2H5 First, you need to figure out the relative ratios of moles of carbon and hydrogen. You do this by first looking up the atomic weight of carbon, hydrogen, and oxygen. Then you use those atomic weights to calculate the molar masses of H2O and CO2. Carbon = 12.0107 Hydrogen = 1.00794 Oxygen = 15.999 Molar mass of H2O = 2 * 1.00794 + 15.999 = 18.01488 Molar mass of CO2 = 12.0107 + 2 * 15.999 = 44.0087 Now using the calculated molar masses, determine how many moles of each product was generated. You do this by dividing the given mass by the molar mass. moles H2O = 11.5 g / 18.01488 g/mole = 0.638361 moles moles CO2 = 22.4 g / 44.0087 g/mole = 0.50899 moles The number of moles of carbon is the same as the number of moles of CO2 since there's just 1 carbon atom per CO2 molecule. Since there's 2 hydrogen atoms per molecule of H2O, you need to multiply the number of moles of H2O by 2 to get the number of moles of hydrogen. moles C = 0.50899 moles H = 0.638361 * 2 = 1.276722 We can double check our math by multiplying the calculated number of moles of carbon and hydrogen by their respective atomic weights and see if we get the original mass of the hydrocarbon. total mass = 0.50899 * 12.0107 + 1.276722 * 1.00794 = 7.400185 7.400185 is more than close enough to 7.40 given rounding errors, so the double check worked. Now to find the empirical formula we need to find a ratio of small integers that comes close to the ratio of moles of carbon and hydrogen. 0.50899 / 1.276722 = 0.398669 0.398669 is extremely close to 4/10, so let's reduce that ratio by dividing both top and bottom by 2 giving 2/5. Since the number of moles of carbon was on top, that ratio implies that the empirical formula for this unknown hydrocarbon is C2H5</span>
3 0
3 years ago
In the laboratory you are asked to make a 0.565 m sodium bromide solution using 315 grams of water. How many grams of sodium bro
Scorpion4ik [409]

Answer : The mass of sodium bromide added should be, 18.3 grams.

Explanation :

Molality : It is defined as the number of moles of solute present in kilograms of solvent.

Formula used :

Molality=\frac{\text{Mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Mass of solvent}}

Solute is, NaBr and solvent is, water.

Given:

Molality of NaBr = 0.565 mol/kg

Molar mass of NaBr = 103 g/mole

Mass of water = 315 g

Now put all the given values in the above formula, we get:

0.565mol/kg=\frac{\text{Mass of NaBr}\times 1000}{103g/mole\times 315g}

\text{Mass of NaBr}=18.3g

Thus, the mass of sodium bromide added should be, 18.3 grams.

6 0
3 years ago
Coefficient -<br> 2) V205<br> Subscript for V<br> Subscript for 0 -<br> HELPPP
Delicious77 [7]

Answer:

there are 2 V's and there are 5 O's

Explanation:

7 0
3 years ago
What is often mistakenly regarded as being based on science?
photoshop1234 [79]
Unless you are talking about one specific theory, the answer is pseudoscience.
3 0
3 years ago
Would nitrogen gas be a mineral if it has a chemical formula of n2?
STALIN [3.7K]

<u>Answer:</u>

Nitrogen gas be a mineral only, if it is in organic forms.

<u>Explanation:</u>

Most of the forms of organic nitrogen is not be taken by plants, with the exception in the form of small organic molecules. Also plants can promptly take the nitrogen  when it is in other forms like ammonia and nitrate.

The microorganisms  in the soil converts the organic forms of nitrogen to mineral form when they decompose organic matters and  also fresh plant residues. This type of process is called mineralisation.

6 0
3 years ago
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