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nevsk [136]
11 months ago
8

When menthol, CH3OH, is burned in the presence of oxygen gas, O2, a large amount of heat energy is released. For this reason, it

is often used as a fuel in high performance racing cars. The combination of methanol has the balanced, thermochemical equation CH3OH(g) + 3/2O2(g) — CO2(g) + 2H2O(1) DeltaH= -764Kj How much methanol, in grams, must be found to produce 701 kj of heat?
Chemistry
1 answer:
Drupady [299]11 months ago
5 0

We have the following balanced equation:

CH_3OH_{(g)}+\frac{3}{2}O_{2\text{ (g)}}\rightarrow CO_{2\text{ (g)}}+2H_2O_{(l)}

They also give us the heat of reaction equal to -764 kJ, i.e. it is an exothermic reaction.

By observing the reaction, we can deduce that for this heat to be generated, one mole of methanol is needed. Now let's see how many grams that mole of methanol equals. We will use the molecular weight equal to 32.04 g/mol

\begin{gathered} g\text{ of methanol = 1 mol }\times\text{ 32.04 g/mol} \\ g\text{ of methanol }=\text{ 32.04 g} \end{gathered}

Now we know the grams of methanol that generate 764 kJ, because the heat of reaction is directly proportional to the mass of the reactants, we can apply a rule of three to know the grams needed to produce a heat of reaction equal to 701 kJ:

\begin{gathered} \frac{32.04\text{ g of methanol}}{764\text{ kJ}}=\text{ }\frac{x\text{ g of methanol}}{701\text{ kJ}} \\ x\text{ g of methanol = }\frac{32.04\text{ g of methanol }\times\text{ 701 kJ}}{764\text{ kJ}} \\ g\text{ of methanol = 29.4 g} \end{gathered}

So, 29.4 g of methanol must be found to produce 701 kJ of heat

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Answer:

We are heating the sample repeatedly to become a pure compound of only MgSO4 (withot H2O) and a constant mass.

Explanation:

Step 1: Data given

Mass of MgSO4·7H2O = 5.06 grams

The remaining MgSO4 had a constant mass of 2.47 grams.

Step 2: Explain why the sample in the crucible was heated repeatedly until the sample had a constant mass.

Before heating the compound has magnesium sulfate and water.

The total mass of this compound is 5.06 grams

By heating we try to eliminate the water.

After heating there remain mgSO4 with a mass of 2.47 grams

This means 5.06 - 2.47 = 2.59 grams is water. All of this is eliminated.

The heating process happens repeatedly to make sure the final compound is pure. So the 2.47 grams os only MgSO4. If the mass would not be constant. It means the compound is not pure, the not all the water is eliminated yet.

So we are heating the sample repeatedly to become a pure compound of only MgSO4 (withot H2O) and a constant mass.

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3 years ago
Physical reactions of carbonyl group​
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Answer:

The polarity of the carbonyl group notably affects the physical properties of melting point and boiling point, solubility, and dipole moment. Hydrocarbons, compounds consisting of only the elements hydrogen and carbon, are essentially nonpolar and thus have low melting and boiling points.

Explanation:

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2 years ago
Which of the following is a transuranium element?<br> Ra<br> Am<br> Tc<br> Pa
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3 years ago
How many grams of hydrochloric acid will react completely with a block of gold is 3.2 cm by 3.8 cm by 2.8 cm, if the density of
JulijaS [17]
Answer:
mass of HCl = 243.5426 grams

Explanation:
1- we will get the mass of the reacting gold:
volume of gold = length * width * height
volume of gold = 3.2 * 3.8 * 2.8 = 34.048 cm^3 = 34.048 ml<span>
density = mass / volume
Therefore:
mass = density * volume
mass of gold = </span>19.3 * 34.048 = 657.1264 grams

2- we will get the number of moles of the reacting gold:
number of moles = mass / molar mass
number of moles = 657.1264 / 196.96657 
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3- we will get the number of moles of the HCl:
First, we will balanced the given equation. The balanced equation will be as follows:
Au + 2HCl ......> AuCl2 + H2
This means that one mole of Au reacts with 2 moles of HCl.
Therefore 3.3362 moles will react with 2*3.3362 = 6.6724 moles of HCL

4- we will get the mass of the HCl:
From the periodic table:
molar mass of H = 1 gram
molar mass of Cl = 35.5 grams
Therefore:
molar mass of HCl = 1 + 35.5 = 36.5 grams/mole
number of moles = mass / molar mass
Therefore:
mass = number of moles * molar mass
mass of HCl = 6.6724 * 36.5
mass of HCl = 243.5426 grams

Hope this helps :)
4 0
3 years ago
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