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il63 [147K]
2 years ago
15

Ned help with this question​

Chemistry
1 answer:
Liula [17]2 years ago
7 0
100/0.25 = 400 cm^3
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A process used to gain knowledge through observation and investigation is?
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Answer:matter

Explanation:

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In which regions of the atmosphere does temperature increase as altitude increases
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Answer:

<h2>stratosphere</h2>
  • In the stratosphere, temperature increases with altitude.
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5 0
3 years ago
Which of the following are second-order reactions? a. C2H6 → 2 CH3 b. 2 N2O5 → 4 NO2 + O2 c. 2 HI → H2 + I2 d. 2 N2O → 2 N2 + O2
Klio2033 [76]

Answer:

The answer is b, c, d, e

Explanation:

b. 2 N2O5 → 4 NO2 + O2

r = k [N2O5]^2 --> Second-order regarding global reaction

c. 2 HI → H2 + I2

r = k [HI]^2 --> Second-order regarding global reaction

d. 2 N2O → 2 N2 + O2

r = k [N2O]^2 --> Second-order regarding global reaction

e. 2 NO2 → 2 NO + O2

r = k [NO2]^2 --> Second-order regarding global reaction

8 0
2 years ago
You have 100 g of Pb(NO3)2. How many moles is this?​
topjm [15]

Answer:

0.302 moles

Explanation:

Data given

Mass of Pb(NO₃)₂ = 100 g

Moles of Pb(NO₃)₂ = ?

Solution:

To find mole we have to know about molar mass of Pb(NO₃)₂  

So,

Molar mass of Pb(NO₃)₂  = 207 + 2[14 + 3(16)]

                                           = 207 + 2[14 + 48]

                                           = 207 + 124

Molar mass of Pb(NO₃)₂  = 331 g/mol

Formula used :

                no. of moles = mass in grams / molar mass

Put values in above formula

                   no. of moles = 100 g / 331 g/mol

                   no. of moles = 0.302 moles

no. of moles of  Pb(NO₃)₂ = 0.302 moles

7 0
3 years ago
What is the mass of 4.99×1021 platinum atoms?
charle [14.2K]

Answer:

\boxed {\boxed {\sf 1.62 \ g \ Pt}}

Explanation:

We are asked to find the mass of a number of platinum (Pt) atoms.

<h3>1. Convert Atoms to Moles </h3>

First, we convert atoms to moles using Avogadro's Number or 6.022 × 10²³. This is the number of particles (atoms, molecules, formula units, etc.) in 1 mole of a substance. In this case, the particles are platinum atoms.

We will convert using dimensional analysis so we set up a ratio using the information we know (6.022 × 10²³ platinum atoms in 1 mole of platinum).

\frac {6.022 \times 10^{23} \ atoms \ Pt}{ 1 \ mol \ Pt}

We are converting 4.99 ×10²¹ atoms of Pt to moles of Pt, so we multiply by this value.

4.99 \times 10^{21} \ atoms \ Pt *\frac {6.022 \times 10^{23} \ atoms \ Pt}{ 1 \ mol \ Pt}

Flip the ratio so the units of atoms of platinum cancel.

4.99 \times 10^{21} \ atoms \ Pt *\frac { 1 \ mol \ Pt}{6.022 \times 10^{23} \ atoms \ Pt}

4.99 \times 10^{21} *\frac { 1 \ mol \ Pt}{6.022 \times 10^{23}}

\frac { 4.99 \times 10^{21}}{6.022 \times 10^{23}} \ mol \ Pt

Divide.

0.008286283627 \ mol \ Pt

<h3>2. Convert Moles to Grams </h3>

Next, we convert moles to grams using the molar mass. This is the mass of 1 mole of a substance. This is found on the Periodic Table because it is equivalent to the atomic mass, but the units are grams per mole instead of atomic mass units. Look up platinum's molar mass.

  • Pt: 195.08 g/mol

Set up another ratio using this new information (195.08 grams of Pt in 1 mole of Pt).

\frac {195.08 \ g \ Pt}{ 1 \ mol \ Pt}

Multiply by the number of moles we just calculated.

0.008286283627 \ mol \ Pt*\frac {195.08 \ g \ Pt}{ 1 \ mol \ Pt}

The units of moles of platinum cancel.

0.008286283627*\frac {195.08 \ g \ Pt}{ 1 }

0.008286283627* {195.08 \ g \ Pt}

1.61648821\ g \ Pt

<h3>3. Round</h3>

The original measurement of atoms ( 4.99 ×10²¹ ) has 3 significant figures, so our answer must have the same. For the number we found, that is the hundredth place. The 6 in the thousandth place tells us to round the 1 up to a 2.

1.62 \ g \ Pt

There are approximately <u>1.62 grams of platinum</u> in 4.99 ×10²¹ atoms of platinum.

8 0
3 years ago
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