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4 years ago

What is the definition of an element?

2 answers:

5 0

<span>A substance that cannot be broken down to simpler substances is called a element. There are 118 different elements. A element is made from only one atom. </span><span />

artcher [175]4 years ago

5 0

An element is a pure substance that cannot be broken down into any simpler substance. They are all located on the periodic table of elements.

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What mass of butane in grams is necessary to produce 1.5×103 kj of heat what mass of co2 is produced?

kari74 [83]

The heat of reaction (i.e. combustion) of butane ( $C_{4} H_{10}$ ) when reacted with oxygen ( $O_{2}$ )  is -2658 kJ/mol butane, and the chemical reaction is given by:

$C_{4} H_{10}$ + $\frac{13}{2} O_{2}$ ---> $4 CO_{2}$ + $5 H_{2}O$

The mass of butane required in the reaction is based on the heat produced by the reaction, which is given to be -1,500 kJ. The minus sign is added because the reaction releases heat (exothermic), which means that the products are in a "lower energy state" than the reactants.

Dividing this with the heat of reaction per mole of butane reacted would give the number of moles butane required. Then, multiplying the answer with the molar mass of butane which is 58 grams/mole, will give the mass of butane required.

Moles of butane = [(-1,500 kJ)/(-2658 kJ/mol butane)]
Moles of butane = 0.5643 moles butane

Mass of butane  = 0.5643 moles butane * 58 grams/mol butane
Mass of butane = 32.73 grams butane

The mass of carbon dioxide ( $CO_{2}$ ) can be determined by multiplying the moles of butane ( $C_{4} H_{10}$ ) with the mole ratio of ( $CO_{2}$ ) produced to the ( $C_{4} H_{10}$ ) reacted, and then with the molar mass of ( $CO_{2}$ ), which is 44 grams/mole.

Mass of carbon dioxide produced
= 0.5643 moles butane * [4 moles $CO_{2}$ / 1 mole $C_{4} H_{10}$ ] * 44 grams/mole $CO_{2}$

Mass of carbon dioxide produced
= 99.32 grams $CO_{2}$

Thus, the mass of butane required is 32.73 grams, and the mass of carbon dioxide produced from the reaction of this amount of butane is 99.32 grams.

4 0

3 years ago

Read 2 more answers

Which is NOT a correct assumption related to the Kinetic Theory?

cestrela7 [59]

Answer:

Explanation:

i took the test and got it right :)

7 0

3 years ago

For the vaporization of a liquid at a given pressure: A.ΔG is positive at all temperatures. B.ΔG is negative at all temperatures

MArishka [77]

Answer:

C. ΔG is positive at low temperatures, but negative at high temperatures (and zero at some temperature).

Explanation:

Since we need to give energy in the form of heat to vaporize a liquid, the enthalpy is positive. In a gas, molecules are more separated than in a liquid, therefore the entropy is positive as well.

Considering the Gibbs free energy equation:

ΔG= ΔH - TΔS

+ +

When both the enthalpy and entropy are positive, the reaction proceeds spontaneously (ΔG is negative) at high temperatures. At low temperatures, the reaction is spontaneous in the reverse direction (ΔG is positive).

5 0

4 years ago

What is the nuclear binding energy for thorium-234? 2.78 × 10-10 J 3.36 × 10-14 J 1.67 × 1017 J 5.35 x 10-23 J

grin007 [14]

The correct option is A.
To calculate the binding energy, you have to find the mass defect first.
Mass defect = [mass of proton and neutron] - Mass of the nucleus
The molar mass of thorium that we are given in the question is 234, the atomic number of thorium is 90, that means the number of neutrons in thorium is
234 - 90 = 144.
The of proton in thourium is 90, same as the atomic number.
Mass defect = {[90 * 1.00728] +[144* 1.00867]} - 234
Note that each proton has a mass of 1.00728 amu and each neutron has the mass of 1.00867 amu.
Mass defect = [90.6552 + 145.24848] - 234 = 1.90368 amu.
Note that the unit of the mass is in amu, it has to be converted to kg
To calculate the mass in kg
Mass [kg] = 1.90368 * [1kg/6.02214 * 10^-26 = 3.161135 * 10^-27
To calculate the binding energy
E = MC^2
C = Speed of light constant = 2.9979245 *10^8 m/s2
E = [3.161135 * 10^-27] * [2.9979245 *10^8]^2
E = 2.84108682069 * 10^-10.
Note that we arrive at this answer because of the number of significant figures that we used.
So, from the option given, Option A is the nearest to the calculated value and is our answer for this problem.

8 0

3 years ago

Read 2 more answers

Which of the following compounds is likely to make the best conductor when

Gnoma [55]

Answer:

c. KBr .

Explanation:

Hello!

In this case, since electrolytes are substances that are able to carry electric current in the form of electrons via ions, those that are ionic are said to have the greatest capacity to conduct the electricity; in such a way, since SO2, C6H12O6 and CO are non-ionic molecules but covalent, they are not good conductor, therefore the best conductor would be c. KBr as it is an ionic compound due to the electronegativity of the K-Br bond.

Best regards!

5 0

3 years ago