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Varvara68 [4.7K]
3 years ago
15

A mechanic repaired 28 cars and 46 trucks last month. He spent 2.5 hours repairing each of these vehicles. Which equation can be

used to find h, the total number of hours the mechanic spent repairing these vehicles?
Chemistry
1 answer:
Simora [160]3 years ago
8 0
28+46 =74(total number of vehicles) 
74 x 2.5 = h(Total number of vehicles x hours spent per vehicle)
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Use standard enthalpies of formation to calculate ΔH∘rxn for the following reaction______.2H2S(g)+3O2(g)→2H2O(l)+2SO2(g) ΔH∘rxn
Ahat [919]

Answer:

-1,103.39KJ/mol

Explanation:

We use the subtract the standard enthalphies of formation of the reactants from that of the products. It must be taken into consideration that the enthalpy of formation of elements and their molecules alone are not taken into consideration. Hence, what we would be considering are the standard enthalpies of formation of H2S, H2O and SO2.

In places where we have more than one mole, we multiply by the number of moles as seen in the balanced chemical equations.

The standard enthalpies of the molecules above are as follows:

H2S = -20.63KJ/mol

H2O = -285.8KJ/mol

SO2 = -296.84KJ/mol

O2 = 0KJ/mol

ΔrH⦵ = [2ΔfH⦵(H2O) + 2 ΔfH⦵(SO2)] − [ΔfH⦵(H2S) + 3

 ΔfH⦵(O2)]

ΔrH⦵ =[(2 × -285.8) + (2 × -296.84)]

-[ 3 × -20.63)]

= (-571.6 - 593.68 + 61.89) = -1,103.39KJ/mol

6 0
4 years ago
A substance that's attracted to water molecules is called
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Hydrophilic molecules
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3 years ago
What is the mass percent of oxygen in sodium bicarbonate (NaHCO3)?
Alenkasestr [34]
The answer is 57.14%.

First we need to calculate molar mass of <span>NaHCO3. Molar mass is mass of 1 mole of a substance. It is the sum of relative atomic masses, which are masses of atoms of the elements.

Relative atomic mass of Na is 22.99 g
</span><span>Relative atomic mass of H is 1 g
</span><span>Relative atomic mass of C is 12.01 g
</span><span>Relative atomic mass of O is 16 g.
</span>
Molar mass of <span>NaHCO3 is:
22.99 g + 1 g + 12.01 g + 3 </span>· <span>16 g = 84 g

Now, mass of oxygen in </span><span>NaHCO3 is:
3 </span>· 16 g = 48 g

mass percent of oxygen in <span>NaHCO3:
48 g </span>÷ 84 g · 100% = 57.14%

Therefore, <span>the mass percent of oxygen in sodium bicarbonate is 57.14%.</span>
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What type of wave do the contractions of the snake muscles make as the snake moves forward
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Rectilinear crawling - Belly scutes are moved forward individually in a wave-like motion. 

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(taken from a user on Yahoo from Correct Answers)
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275 g of a compound with the molecular formula ccl2f2 contains how many molecules of the compound
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