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3 years ago

What is the mass of 2.70 ×10^22 molecules of NaOH (Molar mass = 40.0 g/mol)?

1 answer:

6 0

Data:
Molar Mass of NaOH = 40 g/mol

Solving: According to the Law Avogradro, we have in 1 mole of a substance, 6.02x10²³ atoms/mol or molecules

1 mol -------------------- 6.02*10²³ molecules
y mol -------------------- 2.70*10²² molecules

6.02*10²³y = 0.270*10²³
$y = \frac{0.270*\diagup\!\!\!\!\!\!10^{\diagup\!\!\!\!\!\!23}}{6.02*\diagup\!\!\!\!\!\!10^{\diagup\!\!\!\!\!\!23}}$
$\boxed{y \approx 0.04\:mol}$

Solving: Find the mass value now

40 g ----------------- 1 mol of NaOH
x g ------------- 0.04 mol of NaOH

$x = 40*0.04$
$\boxed{\boxed{x = 1.6\:g}}\end{array}}\qquad\quad\checkmark$

Answer:
The mass is 1.6 grams

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Answer:

molar mass has unit of g/mol so it's usually calculated by taking mass divide by number of moles

but usually, molar masses are given in periodic table itself

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3 years ago

Iron has a density of 7.86 g/cm3. Calculate the volume (in dL) of a piece of iron having a mass of 4.07 kg . Note that the densi

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Answer:

The volume of the piece of iron is 5.18dL.

Explanation:

The density (ρ) is equal to the mass (m) divided the volume (V).

$\rho = \frac{m}{V}$

If we rearrange it, we have:

$V=\frac{m}{\rho }$

To express the volume in dL we will need the following relations:

1 dL = 0.1 L
1 kg = 10³ g
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Then,

$\rho = \frac{7.86g}{cm^{3} } .\frac{1cm^{3} }{1mL} .\frac{1mL}{10^{-3}L } .\frac{1kg}{10^{3}g } =7.86kg/L$

Finally,

$V=\frac{m}{\rho }=\frac{4.07kg}{7.86 kg/L} =0.518L.\frac{1dL}{0.1L} =5.18dL$

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4 years ago

Read 2 more answers

Given the following equation, what would be the theoretical yield in grams of acetylsalicylic acid (C9H8O4) that can be produced

Mariana [72]

Answer:

The correct answer is 2.6 g C₉H₈O₄

Explanation:

-First we have to write and to balance the chemical equation:

C₇H₆O₃ + C₄H₆O₃ ⇄ C₉H₈O₄ + C₂H₄O₂

-Then, we calculate the molecular masses of reactants and products:

1 mol C₇H₆O₃= (12 g/mol C x 7) + (1 g/mol H x 6) + (16 g/mol O x 3)= 138 g

1 mol C₄H₆O₃= (12 g/mol C x 4) + (1 g/mol H x 6) + (16 g/mol O x 3)= 102 g

1 mol C₉H₈O₄= (12 g/mol C x 9) + (1 g/mol H x 8) + (16 g/mol O x 4)= 180 g

1 mol C₂H₄O₂= (12 g/mol C x 2) + (1 g/mol H x 4) + (16 g/mol O x 2)= 60 g

The mass balance is correct because:

mass reactants = mass products

138 g + 102 g = 180 g + 60 g

240 g = 240 g

-Now we use the masses from the chemical equation to calculate how reactant we need. We know that 138 g of salicylic acid (C₇H₆O₃) react with 102 g of acetic anhydride (C₄H₆O₃). So, the grams of acetic anhydride we need to react with 2 g of salicylic acid will be:

138 g C₇H₆O₃------------------- 102 g C₄H₆O₃

2.0 g C₇H₆O₃ -------------------- x= (2.0 x 102)/138 = 1.48 g C₄H₆O₃

If we compare, the amount of C₄H₆O₃ we need (1.48 g) is lesser than the amount we have (8 g), so C₄H₆O₃ is the excess reactant and C₇H₆O₃ is the limiting reactant.

- Finally, we use the limiting reactant to calculate the theoretical yield in grams of C₉H₈O₄. From the chemical equation, we know that 138 g C₇H₆O₃ yield 180 g of C₉H₈O₄. We have 2.0 g, so:

138 g C₇H₆O₃------------------- 180 g C₉H₈O₄

2.0 g C₇H₆O₃ -------------------- x= (2.0 x 180)/138 = 2.6 g C₉H₈O₄

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