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Nina [5.8K]
3 years ago
10

A chemical change has occured if the number of atoms is greater after the reaction than it was before the reaction.

Chemistry
1 answer:
diamong [38]3 years ago
8 0

Answer:

False

Explanation:

It is not correct to assert that a chemical change has occurred if the number of atoms is greater after the reaction than it was before the reaction.

For every chemical reaction, the law of conservation of mass must be strictly adhered.

The law states that "during a chemical reaction, matter is neither created nor destroyed, atoms are simply rearranged".

By the virtue of this law, the number of atoms at the beginning and the end of the reaction must remain the same for this law to be applicable.

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Name 5 metals used to make the penny over the years.
Irina18 [472]
These 5 metals are: zinc,copper,tin,bronze,nickel
6 0
3 years ago
Which molecules are pure elements?
Elenna [48]
Well none since molecules are a group of two or more atoms electrically bonded with one another. However, there are gases that does not naturally bond due to their stability and can be found in nature as pure elements. But these are not considered as molecules.

(By the way, these gases are the noble gases that can be found on the last column of the periodic table) 
8 0
3 years ago
Read 2 more answers
A mixture contains NaHCO3 together with unreactive components. A 1.75 g sample of the mixture reacts with HA to produce 0.561 g
Lynna [10]

Answer:

\%NaHCO_3=61.2\%

Explanation:

Hello.

In this case, since the undergoing chemical reaction is only between the sodium bicarbonate and the acid HA:

NaHCO_3+HA\rightarrow NaA+H_2O+CO_2

For 0.561 g of yielded carbon dioxide (molar mass 44 g/mol), the following mass of sodium bicarbonate (molar mass 84 g/mol) that reacted was:

m_{NaHCO_3}=0.561gCO_2*\frac{1molCO_2}{44gCO_2} *\frac{1molNaHCO_3}{1molCO_2} *\frac{84gNaHCO_3}{1molNaHCO_3} \\\\m_{NaHCO_3}=1.071g

Considering the 1:1 mole ratio between CO2 and NaHCO3. Finally, the percent by mass of NaHCO3 is computed by dividing the mass of reacted NaHCO3 and t the mixture:

\%NaHCO_3=\frac{1.071g}{1.75g}*100\%\\ \\\%NaHCO_3=61.2\%

Best regards.

5 0
3 years ago
A student who stresses too much about his grades has incorrectly named an organic compound 3-propylhexane.
Brums [2.3K]

Answer:

None of these.

The correct answer should be, 4-ethylheptane.

Explanation:

In naming Alkanes, the general rules apply:

I. Identify the longest continuous carbon chain and name it as the root or parent name.

II. Identify any side chains and add their names and positions as a prefix to the parent chain.

III. When there are more than one type of side chain, name them alphabetically.

IV. Use hyphens between numbers and letters and commas between numbers.

V. Number your side chains to obtain the lowest number combinations possible.

For the above question,

first, attempt drawing only the carbon skeleton, of 3-propylhexane thus,

C-C-C-C-C-C

|

C-C-C

The longest continuous carbon chain (numbering from the top right) is 7 carbon atoms, hence, parent or root name is heptane. The 2 carbon atoms (at top left) not numbered make up the alkyl group called ethyl and since they are attached to carbon number 4 of the numbered carbon atoms ( whether the numbering is from top right to bottom right or vice versa ), their position and name should be written as a prefix to the parent name. That is why the organic compound is named, 4-ethylheptane.

Please note that in drawing the carbon skeleton of 3-propylhexane, the name is the same even if you start placing the bottom 3 carbon atoms on the 3rd carbon (top) from the left or from the right because the numbering can start from any side to achieve the lowest number combinations of numbering common Alkanes.

7 0
3 years ago
A student has two samples of NaCl, each one from a different source. Assume that the only potential contaminant in each sample i
bija089 [108]

Answer:

The correct option is;

A. Which sample has the higher purity

Explanation:

The information given relate to the presence of two samples of NaCl, from different sources

The only potential contaminant in each of the sources = KCl

The content of the sample = NaCl

The molar mass of NaCl = 58.44 g/mol

The molar mass of KCl = 74.5513 g/mol

Let the number of moles of KCl in the sample = X

For a given mass of NaCl, KCl mixture, we have;

The molar mass of potassium = 39.0983 g/mol

The molar mass of chlorine = 35.453 g/mol

The molar mass of sodium ≈ 23 g/mol

Therefore;

Each mole of KCl, will yield 35.453 g/mol per 74.5513 g/mol of KCl

While each mole of NaCl will yield 35.453 g/mol per 58.44 g/mol of NaCl

Therefore, the pure sodium chloride sample will yield more chlorine per unit mass of sample.

As such if the two samples have the same mass, the sample with the contaminant of KCl will yield less mass of chlorine per unit mass of the sample, from which the student will be able to tell the purity of the solution.

The sample with the higher purity will yield  a higher mass chlorine per unit mass of the sample.

6 0
3 years ago
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