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3 years ago

3.

Chemistry

1 answer:

Vsevolod [243]3 years ago

3 0

Answer:

2 half-lives=0.8

6 half-lives= 0.05

Explanation

Half-lives are constant and always decrease by half, implying that the concentration decreases by half at a consistent rate.

3.2/2= 1.6/2= 0.8 is two half-lives

3.2/2= 1.6/2= 0.8/2= 0.4/2= 0.2/2= 0.1/2=0.05 is six half-lives

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Which of the possible compounds has a mass of 163 grams when

Simora [160]

Answer:

CH4

Explanation:

In solving this problem, we must remember that one mole of a compound contains Avogadro's number of elementary entities. These elementary entities include atoms, molecules, ions etc. Recall that one mole of a substance is the amount of substance that contains the same number of elementary entities as 12g of carbon-12. The Avogadro's number is 6.02 × 10^23.

Hence we can now say;

If 163 g of the compound contains 6.13 ×10^24 molecules

x g will contain 6.02 × 10^23 molecules

x= 163 × 6.02 × 10^23 / 6.13 × 10^24

x= 981.26 × 10^23/ 6.13 ×10^24

x= 160.1 × 10^-1 g

x= 16.01 g

x= 16 g(approximately)

16 g is the molecular mass of methane hence x must be methane (CH4)

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3 years ago

Are the changes from a to b and from b to c physical or chemical changes?

Vitek1552 [10]

Answer:

They are physical changes.

Explanation:

This is because there in no chemical reaction taking place, just a physical change.

A physical change in a change in which the chemical structure of the substance does not change. Ice, water and steam are all the same on a molecular level, thus changing from ice to water or from water to steam are physical changes.

A chemical change is a change in which the chemical structure of the substance undergoes a change, since this does not happen going for A to B or B to C they are not chemical changes.

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3 years ago

A chemist reacted 17.25 grams of sodium metal with an excess amount of chlorine gas. The chemical reaction that occurred is show

Afina-wow [57]

Answer: The actual yield of the product is 38.57 g

Explanation:

The number of moles is defined as the ratio of the mass of a substance to its molar mass. The equation used is:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ ......(1)

We are given:

Given mass of Na = 17.25 g

Molar mass of Na = 23 g/mol

Putting values in equation 1, we get:

$\text{Moles of Na}=\frac{17.25g}{23g/mol}=0.75mol$

For the given chemical reaction:

$2Na+Cl_2\rightarrow 2NaCl$

By stoichiometry of the reaction:

2 moles of Na produces 2 moles of NaCl

So, 0.75 moles of Na will produce = $\frac{2}{2}\times 0.75=0.75mol$ of NaCl

We know, molar mass of $NaCl$ = 58.44 g/mol

Putting values in above equation, we get:

$\text{Mass of NaCl}=(0.75mol\times 58.44g/mol)=43.83g$

The percent yield of a reaction is calculated by using an equation:

$\% \text{yield}=\frac{\text{Actual value}}{\text{Theoretical value}}\times 100$ ......(1)

Given values:

Percent yield of the product = 88 %

Theoretical value of the product = 43.83 g

Plugging values in equation 1:

$88\% =\frac{\text{Actual yield}}{43.83g}\times 100\\\\\text{Actual yield}=\frac{88\times 43.83}{100}=38.57g$

Hence, the actual yield of the product is 38.57 g

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3 years ago

8) Which one of the following can be broken down in to simpler substances

Sophie [7]

Answer:

Compounds can be broken down into simpler substances by chemical means, but elements cannot. break a compound into simpler substances; oxygen and hydrogen that water contains.

But where is the following?

3 0

3 years ago

Please help as soon as possible!

Keith_Richards [23]

Answer:

4 because CoCO2 is in a degree And it’s all four different elements

7 0

3 years ago

Read 2 more answers