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4 years ago

An unknown is discovered to have three isotopes. 25% have a mass of 86.0, 66% have a

Chemistry

1 answer:

7nadin3 [17]4 years ago

7 0

It’s obvious that it’s 13 because 89 - 92 =13

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This gas is found in the stratosphere where it helps protect us from UV radiation.

Luba_88 [7]

Answer: A

Explanation:

3 0

3 years ago

Number of electrons present in 3.6mg of NH₄⁺?

nata0808 [166]

0.0036g of NH4+ x 1mol of NH4+/18.04g of NH4+ x 6.02*10^23 electrons of NH4+/1mol of NH4+

= 1.20 x 10^20 electrons of NH4+

4 0

3 years ago

A sample of CO2 weighing 86.34g contains how many molecules?

irakobra [83]

Answer:

1.181 × 10²⁴ molecules CO₂

General Formulas and Concepts:

Chemistry - Atomic Structure

Reading a Periodic Table
Using Dimensional Analysis
Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

Explanation:

Step 1: Define

86.34 g CO₂

Step 2: Identify Conversion

Avogadro's Number

Molar Mass of C - 12.01 g/mol

Molar Mass of O - 16.00 g/mol

Molar Mass of CO₂ - 12.01 + 2(16.00) = 44.01 g/mol

Step 3: Convert

$86.34 \ g \ CO_2(\frac{1 \ mol \ CO_2}{44.01 \ g \ CO_2} )(\frac{6.022 \cdot 10^{23} \ molecules \ CO_2}{1 \ mol \ CO_2} )$ = 1.18141 × 10²⁴ molecules CO₂

Step 4: Check

We are given 4 sig figs. Follow sig fig rules and round.

1.18141 × 10²⁴ molecules CO₂ ≈ 1.181 × 10²⁴ molecules CO₂

4 0

3 years ago

a 0.555 g sample of mayonnase was burned in excess oxygen inside a bomb calorimeter with a total heat capacity (bomb and water)

Fofino [41]

Answer:

$Dietary\ Calories=65.6kcal$

Explanation:

Hello!

In this case, since we can see that the heat released by the combustion of the mayonnaise is absorbed by the bomb calorimeter and water, we can set up the following equation:

$m_{mayonnaise}q_{mayonnaise}=C\Delta T$

Whereas q for mayonnaise stands for the heat due to its usage; thus, we plug in to obtain:

$q_{mayonnaise}=\frac{5.20kJ/\°C*2.93\°C}{0.555g} \\\\q_{mayonnaise}=27.45\frac{kJ}{g}$

Now, if 10.0 g are eaten, the energy provided by it turns out:

$E_{mayonnaise}=27.45kJ/g*10.0g\\\\E_{mayonnaise}=274.5kJ$

And we need that value in dietary calories, 1 kcal:

$Dietary\ Calories=274.52kJ*\frac{1kcal}{4.184kJ}\\\\ Dietary\ Calories=65.6kcal$

Best regards!

4 0

3 years ago

How many moles are present in 54.8 mL of mercury if the density of mercury is 13.6 g/mL?

lesya692 [45]

Answer:

3.72 mol Hg

General Formulas and Concepts:

Chemistry - Atomic Structure

Reading a Periodic Table
Using Dimensional Analysis
Density = Mass over Volume

Explanation:

Step 1: Define

D = 13.6 g/mL

54.8 mL Hg

Step 2: Identify Conversions

Molar Mass of Hg - 200.59 g/mol

Step 3: Find

13.6 g/mL = x g / 54.8 mL

x = 745.28 g Hg

Step 4: Convert

$745.28 \ g \ Hg(\frac{1 \ mol \ Hg}{200.59 \ g \ Hg} )$ = 3.71544 mol Hg

Step 5: Check

We are given 3 sig figs. Follow sig fig rules and round.

3.71544 mol Hg ≈ 3.72 mol Hg

8 0

3 years ago