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When using science to investigate physical phenomena, which characteristic of the event must exist?

Maru [420]

"Observable" is the one characteristic of event that must exist when using science to investigate physical phenomena.

5 0

2 years ago

To calculate the enthalpy change for the reaction, 2CO (g) + O2 (g) Imported Asset 2 CO2 (g), you can use ΔHf0 values for each r

svetoff [14.1K]

Answer:

ΔH0reaction = [ΔHf0 CO2(g)] - [ΔHf0 CO(g) + ΔHf0 O2(g)]

Explanation:

Chemical equation:

CO + O₂ → CO₂

Balanced chemical equation:

2CO + O₂ → 2CO₂

The standard enthalpy for the formation of CO = -110.5 kj/mol

The standard enthalpy for the formation of O₂ = 0 kj/mol

The standard enthalpy for the formation of CO₂ = -393.5 kj/mol

Now we will put the values in equation:

ΔH0reaction = [ΔHf0 CO2(g)] - [ΔHf0 CO(g) + ΔHf0 O2(g)]

ΔH0reaction = [-393.5 kj/mol] - [-110.5 kj/mol + 0]

ΔH0reaction = [-393.5 kj/mol] - [-110.5 kj/mol]

ΔH0reaction = -283 kj/mol

7 0

2 years ago

Cells which form pathways to and from the brain are .epiltheilal neurons connnective

nikdorinn [45]

Answer:

neurons

Explanation:

The long-axoned cells, called principal neurons, transmit information over long distances from one brain region to another (Sheperd,1979). Principal neurons provide the pathways of communication within the nervous system.

3 0

2 years ago

Read 2 more answers

Toluene (C6H5CH3 ), an organic compound often used as a solvent in paints, is mixed with a similar organic compound, benzene (C6

Sergeeva-Olga [200]

Explanation:

The given data is as follows.

Weight of solute = 75.8 g, Molecular weight of solute (toulene) = 92.13 g/mol, volume = 200 ml

Therefore, molarity of toulene is calculated as follows.

Molarity = $\frac{\text{weight of solute}}{\text{molecular weight of solute}} \times \frac{1000}{\text{volume of solution in ml}}$

= $\frac{75.8 g}{92.13 g/mol} \times \frac{1000}{200 ml}$

= 4.11 M

Hence, molarity of toulene is 4.11 M.

As molality is the number of moles of solute present in kg of solvent.

So, we will calculate the molality of toulene as follows.

Molality = $\frac{\text{given weight of solute}}{\text{given molecular weight of solute}} \times \frac{1000}{\text{weight of solvent in grams}}$

= $\frac{75.8 g}{92.13 g/mol} \times \frac{1000}{95.6 g}$

= 8.6 m

Hence, molality of given toulene solution is 8.6 m.

Now, calculate the number of moles of toulene as follows.

No. of moles = $\frac{mass}{\text{molar mass}}$

= $\frac{75.8 g}{92.13 g/mol}$

= 0.8227 mol

Now, no. of moles of benzene will be as follows.

No. of moles = $\frac{mass}{\text{molar mass}}$

= $\frac{95.6 g}{78.11 g/mol}$

= 1.2239 mol

Hence, the mole fraction of toulene is as follows.

Mole fraction = $\frac{\text{moles of toulene}}{\text{total moles}}$

= $\frac{0.8227 mol}{(0.8227 + 1.2239) mol}$

= 0.402

Hence, mole fraction of toulene is 0.402.

As density of given solution is 0.857 $g/cm^{3}$ so, we will calculate the mass of solution as follows.

Density = $\frac{mass}{volume}$

0.857 $g/cm^{3}$ = $\frac{mass}{200 ml}$ (As 1 $cm^{3}$ = 1 g)

mass = 171.4 g

Therefore, calculate the mass percent of toulene as follows.

Mass % = $\frac{\text{mass of solute}}{\text{mass of solution}} \times 100$

= $\frac{75.8 g}{171.4 g} \times 100$

= 44.22%

Therefore, mass percent of toulene is 44.22%.

8 0

3 years ago

Which reaction is a decomposition reaction? A. 2KClO3 → 2KCl + 3O2 B. 4Na + O2 → 2Na2O C. ZnS + 3O2 → 2ZnO + 2SO2 D. 2NaBr + CaF

Vedmedyk [2.9K]

Answer:

Option A. 2KClO₃ → 2KCl + 3O₂

Explanation:

There are five basic general types of chemical reactions:

Decomposition reactions

Synthesis or combination reaction

Single replacement reactions

Double replacement reactions

Combustion reactions

The given reactions are:

2KClO₃ → 2KCl + 3O₂

Which is, indeed, a decomposition reaction because the reactant, KClO₃, is a single substance that undergoes a reaction in which it yields two new substances, known as products: KCl and O₂.

4Na + O₂ → 2Na₂O is a synthesis or combination reaction because two reactants, Na and O₂, combine for the formation of one single new product, Na₂O.

ZnS + 3 O₂ → 2ZnO + 2SO₂ is a single replacement reaction because oxygen is replacing Zn and S in ZnS to form ZnO and plus SO₂.

2NaBr + CaF₂ → 2NaF + CaBr₂ is a double replacement reaction because two ions (Br⁻ from NaBr and F⁻ from CaF₂) are exchanging places with other two ions (Na⁺ from NaBr and Ca²⁺ from CaF₂) two form two new ionic compounds (NaF and CaBr₂).

4 0

2 years ago