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2 years ago

What is a chemical change?

1 answer:

5 0

A chemical change, also known as a chemical reaction, is a process in which one or more substances are altered into one or more new and different substances. In other words, a chemical change is a chemical reaction involving the rearrangement of atoms.

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What was alchemy?

stira [4]

Answer:

Explanation:

its a very old study and philosophy of how to change basic substances such as metals into other substances

8 0

2 years ago

Read 2 more answers

Which of the following equations represent

Harrizon [31]

Answer:

a. MgO(s) + H2CO3(aq) → MgCO3(s) + H2O(l) DOUBLE DISPLACEMENT REACTION.

b. 2KNO3(s)→2KNO2 (s) + O2(8) DESCOMPOSITION REACTION.

c. H2(g) + CuO(s) → Cu(s) + H2O(1) SINGLE DISPLACEMENT REACTION.

d. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(1) COMBUSTION REACTION.

e. H2(8) + Cl2(g) → 2HCl(8) SYNTHESIS REACTION.

f. SO3(g) + H2O(1)→ H2SO4(aq) SYNTHESIS REACTION.

5 0

2 years ago

. Through what three mechanisms do gamma rays interact with matter?

siniylev [52]

Answer:

Photoelectric effect, pair production and Compton scattering

Explanation:

Gamma rays, having no charge, can be slowed slowly by ionization as a material passes through. They suffer other mechanisms that eventually make them disappear, transferring their energy, they can cross several centimeters of a solid, or hundreds of meters of air, without undergoing any process or affecting the material they cross. Then they suffer one of the three effects and deposit much of their energy there. The three mechanisms of interaction with matter are: the photoelectric effect, the Compton effect and the production of pairs.

The photoelectric effect is that the photon meets an electron in the material and transfers all its energy, disappearing the original photon. The secondary electron acquires all the energy of the photon in the form of kinetic energy, and is sufficient to separate it from its atom and convert it into a projectile. This is stopped by ionization and excitation of the material

In the Compton effect the photon collides with an electron as if it were a clash between two elastic spheres. The secondary electron acquires only part of the energy of the photon and the rest takes it with another photon of lesser energy and diverted.

When an energy photon approaches the intense electric field of a nucleus, the production of pairs can happen. In this case the photon is transformed into an electron positron pair. Since the sum of the mass of the pair is 1.02 MeV, it cannot happen if the photon's energy is less than this amount. If the energy of the original photon is greater than 1.02 MeV, the surplus is distributed by the electron and the positron as kinetic energy, and the material can be ionized. The positron at the end of its path forms a positronium and then annihilates producing two annihilation photons, 0.51 MeV each.

3 0

2 years ago

The equilibrium constant for the reaction AgBr(s) Picture Ag+(aq) + Br− (aq) is the solubility product constant, Ksp = 7.7 × 10−

barxatty [35]

Answer:

The reaction will be non spontaneous at these concentrations.

Explanation:

$AgBr(s)\rightarrow Ag^+(aq) + Br^- (aq)$

Expression for an equilibrium constant $K_c$ :

$K_c=\frac{[Ag^+][Br^-]}{[AgCl]}=\frac{[Ag^+][Br^-]}{1}=[Ag^+][Br^-]$

Solubility product of the reaction:

$K_{sp}=[Ag^+][Br^-]=K_c=7.7\times 10^{-13}$

Reaction between Gibb's free energy and equilibrium constant if given as:

$\Delta G^o=-2.303\times R\times T\times \log K_c$

$\Delta G^o=-2.303\times R\times T\times \log K_{sp}$

$\Delta G^o=-2.303\times 8.314 J/K mol\times 298 K\times \log[7.7\times 10^{-13}]$

$\Delta G^o=69,117.84 J/mol=69.117 kJ/mol$

Gibb's free energy when concentration $[Ag^+] = 1.0\times 10^{-2} M$ and $[Br^-] = 1.0\times 10^{-3} M$

Reaction quotient of an equilibrium = Q

$Q=[Ag^+][Br^-]=1.0\times 10^{-2} M\times 1.0\times 10^{-3} M=1.0\times 10^{-5}$

$\Delta G=\Delta G^o+(2.303\times R\times T\times \log Q)$

$\Delta G=69.117 kJ/mol+(2.303\times 8.314 Joule/mol K\times 298 K\times \log[1.0\times 10^{-5}])$

$\Delta G=40.588 kJ/mol$

For reaction to spontaneous reaction: $\Delta G$ .
For reaction to non spontaneous reaction: $\Delta G>0$ .

Since ,the value of Gibbs free energy is greater than zero which means reaction will be non spontaneous at these concentrations

5 0

2 years ago

a mixture of carbon and sulfur has a mass of 9.0 g. complete combustion with excess o2 gives 22.5 g of a mixture of co2 and so2.

photoshop1234 [79]

S + O2 → SO2
z / (32.0655 g S/mol) x (1 mol SO2 / 1 mol S) x (64.0638 g SO2/mol) = (1.9979 z) g SO2 

C + O2 → CO2 
(9.0-z) / (12.01078 g C/mol) x (1 mol CO2 / 1 mol C) x (44.00964 g CO2/mol) = (32.9776 - 3.66418 z) g CO2 

Add the two masses of SO2 and CO2 and set them equal to the amount given in the problem: 
(1.9979 z) + (32.9776 - 3.66418 z) = 27.9 
Solve for z algebraically: 
z = 3.0 g S

7 0

2 years ago