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4 years ago

Which is the first step in an arson investigation that helps reconstruct the fire?

Chemistry

2 answers:

Tamiku [17]4 years ago

8 0

C. taking samples of ignition source.

expeople1 [14]4 years ago

6 0

Answer is: <span>B. taking photographs.
</span>Fire scene investigation begins when investigator approaches the location and start observing the scene from a distance and begin photographing. That must be done first because crowd start gathering. Once the fire scene is secured, w<span>intesses can be interviewed.</span>

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Chlorine gas can be prepared in the laboratory by the reaction of hydrochloric acid with manganese(IV) oxide. 4 HCl ( aq ) + MnO

Leno4ka [110]

Answer:

1. HCl is the limiting reactant.

2. The theoretical yield of Cl2 is 23.197g

3. The Actual yield 19.787g

Explanation:

4HCl + MnO2 —> MnCl2 + 2H2O + Cl2

First let us calculate the number of mole of HCl and MnO2.

Molar Mass of HCl = 1 + 35.5 = 36.5g/mol

Mass of HCl = 47.7g

Number of mole = Mass /Molar Mass

Number of mole of HCl = 47.7/36.5 = 1.31mole

Molar Mass of MnO2 = 35 + (2x16) = 35 + 32 = 67g/mol

Mass of MnO2 = 40.5g

Number of mole = Mass /Molar Mass

Number of mole of MnO2 = 40.5/67 = 0.60mole

From equation,

4moles of HCl required 1mole of MnO2. Now let us consider the following:

4moles HCl require 1mole MnO2. Therefore 0.31mol of HCl will require = 0.31/4 = 0.0775mole of MnO2. This amount is little compared to the amount of MnO2 ( i.e 0.60mol) calculated. Therefore, HCl is the limiting reactant.

2. 4HCl + MnO2 —> MnCl2 + 2H2O + Cl2

Molar Mass of HCl = 36.5g/mol

Mass of HCl from the balanced equation = 4 x 36.5 = 146g

Molar Mass of Cl2 = 2 x 35.5 = 71g/mol

From the equation,

146g of HCl produced 71g of Cl2.

Therefore, 47.7g of HCl will produce = (47.7x 71)/146 = 23.197g of Cl2.

The theoretical yield of Cl2 is 23.197g

3. %yield = 85.3%

Theoretical yield = 23.197g

Actual yield =?

%yield = Actual yield /Theoretical yield

Actual yield = %yield x theoretical yield

Actual yield = 85.3% x 23.197g = (85.3/100) x 23.197 = 19.787g

5 0

3 years ago

PLEASE HELP!!

kondaur [170]

Number of moles of HCl = $\frac{mass (g)}{molar mass}$
= $\frac{27.8 g}{36.45}$ = 0.763 mole
From balanced equation:
4 moles of HCl give 2 moles Cl2
0.763 mole HCl give ?? mole Cl2
by cross multiplication :
= 0.38 mole Cl2
mass of Cl2 = moles x molar mass = 0.38 x 70.9 = 27 g

3 0

4 years ago

Read 2 more answers

When 1 mole of carbon is burned, carbon dioxide is produced, and 393 kilojoules (kJ) of energy are released. If this reaction is

EleoNora [17]

The energy of 393 kJ is released as heat. Then, the container will experience an increase of temperature and, given that it is sealed, also an increase of pressure.

The increase of temperature results from the heat developed during the reaction.

The increase of pressure results from the fact that that the solid carbon will become gaseuos carbon dioxide. This gas will occupy a larger volume than the solid carbon and also this elevation of the temperature will make the pressure of the gas inside the container increase.

7 0

3 years ago

Why does the rate of the reaction decrease over time? Why does the rate of the reaction decrease over time? Exothermic reactions

fgiga [73]

Answer: The rate of the reaction decrease over time as the reaction proceeds, a decrease in the concentration of reactants results in fewer successful collisions.

Explanation:

Rate of a reaction is defined as the change in concentration of products and reactants with respect to time.

The rate of a reaction decreases with times because reactants are converting into products.

As a result, the reaction is proceeding with a decrease in the concentration of reactants due to which less number of collisions between the reactant molecules will be there.

Hence, rate of reaction will decrease.

Thus, we can conclude that the rate of the reaction decrease over time as the reaction proceeds, a decrease in the concentration of reactants results in fewer successful collisions.

3 0

3 years ago

In mitosis, how does a daughter cell compare with its parent cell?

lyudmila [28]

Answer: im pretty sure its the last (one daughter cell has no similarity to its parent cell.)

Explanation: bc a daughter cell has 30 and the parent cell would have 46 and thats not twice or half as many and they arent the same either so the last one makes sences

6 0

3 years ago