The one factor that a scientist changes in an experiment is called the

Which of the following processes absorbs energy? A) condensation of water on a wind shield of a car B) formation of copperC) bal

Alecsey [184]

Answer:

C) ball rollinflown a hill

Explanation:

The question asks to identify the endothermic process in the list of options. By way of elimination, we have;

A) condensation of water on a wind shield of a car

Condensation is an exothermic process. That is, heat is given out as the gases change into the liquid state of matter.

B) formation of copper

This is an exothermic process. Capture of electrons by a cation is always exothermic.

C) ball rollinflown a hill

This is the correct option. Energy is absorbed by the ball as it moves on the hill

D) formation of ice from liquid water

Freezing is an example of exothermic reaction. Heat is given off to the surroundings.

E) oxide from copper and oxygen

Formation of metal oxides and most reactions involving oxygen are exothermic reactions,

4 0

3 years ago

When utilizing a transmission electron microscope, why is it necessary to stain the specimen with heavy metal salts?

Schach [20]

Staining specimen with heavy metal salts (e.g. tungsten, molybdenum) allows you to see the specimen better with higher contrast when electron beam deflects off of your sample.

6 0

3 years ago

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The useful metal manganese can be extracted from the mineral rhodochrosite by a two-step process.... In the first step, manganes

frez [133]

Answer : The mass of $MnCO_3$ required are, 35 kg

Explanation :

First we have to calculate the mass of $MnO_2$ .

The first step balanced chemical reaction is:

$2MnCO_3+O_2\rightarrow 2MnO_2+2CO_2$

Molar mass of $MnCO_3$ = 115 g/mole

Molar mass of $MnO_2$ = 87 g/mole

Let the mass of $MnCO_3$ be, 'x' grams.

From the balanced reaction, we conclude that

As, $(2\times 115)g$ of $MnCO_3$ react to give $(2\times 87)g$ of $MnO_2$

So, $xg$ of $MnCO_3$ react to give $\frac{(2\times 87)g}{(2\times 115)g}\times x=0.757xg$ of $MnO_2$

And as we are given that the yield produced from the first step is, 65 % that means,

$60\% \text{ of }0.757xg=\frac{60}{100}\times 0.757x=0.4542xg$

The mass of $MnO_2$ obtained = 0.4542x g

Now we have to calculate the mass of $Mn$ .

The second step balanced chemical reaction is:

$3MnO_2+4Al\rightarrow 3Mn+2Al_2O_3$

Molar mass of $MnO_2$ = 87 g/mole

Molar mass of $Mn$ = 55 g/mole

From the balanced reaction, we conclude that

As, $(3\times 87)g$ of $MnO_2$ react to give $(3\times 55)g$ of $Mn$

So, $0.4542xg$ of $MnO_2$ react to give $\frac{(3\times 55)g}{(3\times 87)g}\times 0.4542x=0.287xg$ of $Mn$

And as we are given that the yield produced from the second step is, 80 % that means,

$80\% \text{ of }0.287xg=\frac{80}{100}\times 0.287x=0.2296xg$

The mass of $Mn$ obtained = 0.2296x g

The given mass of Mn = 8.0 kg = 8000 g (1 kg = 1000 g)

So, 0.2296x = 8000

x = 34843.20 g = 34.84 kg = 35 kg

Therefore, the mass of $MnCO_3$ required are, 35 kg

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3 years ago

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The ionization of pure water forms _____.

Evgesh-ka [11]

Answer: The ionization of pure water forms <u><em>hydroxide and hydronium ions.</em></u>

Explanation:

Ionization is a reaction in the pure water in which water breaks down into its constituting ions that hydronium ion and hydroxide ions.

$H_2O+H_2O\rightleftharpoons H_3O^++OH^-$

One molecule of water looses its proton to form hydroxide ion and l=the lost protons get associated with another water molecule to form hydronium ion.

4 0

3 years ago

A neutral atom of Cl-37 has

Ostrovityanka [42]

Answer:

17 protons, 20 neutrons, and 17 electrons.

Explanation:

A periodic table can be defined as the standard arrangement of chemical elements by atomic number, electronic configuration and chemical properties in a tabular form.

Generally, a proper representation of the mass number and atomic number of chemical elements is key and very important in chemistry.

Furthermore, as a rule, it should be noted that the mass number (nucleon number) is always larger than the atomic number(number of proton).

The mass number of this neutral atom of Cl-37 is 37 and we know that the atomic number (number of protons) of chlorine is 17. Also, the atomic number of an element is equal to the number of its electrons.

A neutral atom of Cl-37 has 17 protons, 20 neutrons, and 17 electrons.

Hence, a neutral atom of Cl-37 can be identified based on its number of protons because it represent its atomic number, which is what is used to differentiate an atom of an element from the atom of another chemical element.

6 0

3 years ago