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mezya [45]
2 years ago
14

How many moles of Si are in 78.0 grams of silicon

Chemistry
2 answers:
Igoryamba2 years ago
8 0

Answer:

\boxed {\boxed {\sf 2.78 \ mol \ Si}}}

Explanation:

To convert from grams to moles, we must use the molar mass. This number can be found on the Periodic Table.

  • Si (Silicon): 28.085 g/mol

We can use number as a ratio.

\frac { 28.085 \ g \ Si}{ 1  \ mol \ Si}

Multiply by the given number of grams.

78.0 \ g \ Si *\frac { 28.085 \ g \ Si}{ 1  \ mol \ Si}

Flip the fraction so the grams of silicon cancel.

78.0 \ g \ Si *\frac {1  \ mol \ Si }{ 28.085 \ g \ Si}

78.0  *\frac {1  \ mol \ Si }{ 28.085 }

\frac {78.0  \ mol \ Si }{ 28.085 }= 2.77728324729 \ mol \ Si

The original number of grams (78.0) has 3 significant figures, so our answer must have the same. For the number of moles calculated, that is the hundredth place. The 7 in the thousandth place tells us to round the 7 to a 8.

2.78 \ mol \ Si

There are about 2.78 moles of silicon in 78.0 grams.

gladu [14]2 years ago
6 0
The answer is 2.78 moles of Si

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The forensic technician at a crime scene has just prepared a luminol stock solution by adding 16.0 g of luminol to H2O creating
san4es73 [151]

Answer : The concentration of luminol in the solution is, 1.20 M.

Explanation : Given,

Mass of luminol = 16.0 g

Volume of solution = 75.0 mL

Molar mass of luminol = 177.16 g/mole

Molarity : It is defined as the number of moles of solute present in one liter of volume of solution.

Formula used :

\text{Molarity}=\frac{\text{Mass of luminol}\times 1000}{\text{Molar mass of luminol}\times \text{Volume of solution (in mL)}}

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

\text{Molarity}=\frac{16.0g\times 1000}{177.16g/mole\times 75.0mL}=1.20mole/L=1.20M

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4 0
3 years ago
Consider the following data on some weak acids and weak bases
SpyIntel [72]

Answer:

b < c < a < d

Explanation:

The weak acid with the lowest pKa will be the most acidic. In the other way, the conjugate base which the acid is weak will be strong.

The weak base with the lowest pKb will be the most basic. And the conjugate base of the weak base will be a strong acid.

Ka Acetic acid = 1.8x10-5

Ka HCN = 1.9x10-10

Kb pyridine = 1.7x10-9

Kb NH3 = 1.8x10-5

NH4Br is the conjugate base of a weak base. That means is a strong acid.

NH4Br has the lowest pH

NaBr is the conjugate base of a strong acid, HBr. That means NaBr is neutral

The most basic between the conjugate base of the acetic acid, NaCH3CO2 and KCN is KCN because the acetic acid is the stronger acid regard to HCN.

The rank is:

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<h3>b < c < a < d</h3>
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A small positively charged nucleus surrounded by revolving negatively charged electrons in fixed orbits

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How many grams of sulfur are required in the preparation of 35.7 moles of sulfur dioxide Sg + O2 SO2​
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Its balanced already

So

  • 1 mol SO_2 require 1 mole sulphur
  • 35.7moles require 35.7mol sulphur

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6 0
2 years ago
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