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3 years ago

15

An atom of lithium-7 has an equal number of(1) electrons and neutrons(2) electrons and protons(3) positrons and neutrons(4) posi

trons and protons

1 answer:

agasfer [191]3 years ago

3 0

Answer: Electrons and protons

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Please help ASAP, chemistry question. I’ll make your answer the BRAINLIEST. Thanks (picture attached)

Naddika [18.5K]

Answer:

Electrochemical Cell

Explanation:

An electrochemical cell is a device that can generate electrical energy from the chemical reactions occurring in it, or use the electrical energy supplied to it to facilitate chemical reactions in it. These devices are capable of converting chemical energy into electrical energy, or vice versa.

7 0

4 years ago

What property can be used to determine if a sample is a pure substance or a mixture?

Yuliya22 [10]

Answer:

Melting point

Explanation:

Pure substances have sharp melting and boiling points while impurities lower the melting point and raise the boiling point

7 0

3 years ago

I need chemistry help! How would I set up these problems?

Bond [772]

Answer: -

1) 8.33 minutes

2) 118.39 in/ s

180.43 m/min

10.83 km/ hr

Explanation: -

Speed of light = 3 x 10⁸ m/s

Distance of the earth from the sun= 93 million miles

We know 1 million = 1,000,000

Also 1 mile = 1609 m

Distance of the earth from the sun= 93 million miles

= 93,000,000 miles.

= 1.5 x $10^{11}$ m

Time taken = $\frac{Distance}{Speed}$

= $\frac{1.5 x [tex] 10^{11}$ m}{3 x 10⁸ m/s} [/tex]

= 500 s

= 500/ 60

= 8.33 minutes

2) Distance = 1 mile = 63360 inches

Time taken = 8.92 min

= 8.92 x 60

= 535.2 s

Speed = $\frac{distance}{time}$

= $\frac{63360 inches}{535.2 s}$

= 118.39 in/ s

Distance = 1 mile = 63360 inches = 63360 x 2.54 cm = 63360 x 2.54 x $10^{-2}$ m

Time taken = 8.92 min

Speed = $\frac{distance}{time}$

= $\frac{63360 x 2.54 x [tex] 10^{-2}$ m}{8.92 min} [/tex]

= 180.43 m/ min

1 m = 10⁻³ Km

1 min = 1/60 hour

1 m /min = 10⁻³ km/ $\frac{1}{60 hour}$

= 60/1000

=0.06 km/hr

180.43 m / min = 180 x 0.06 km / hr

= 10.93 km / hr

4 0

3 years ago

Which of the following does NOT indicate that a chemical change may have taken place?

labwork [276]

The following does NOT indicate that a chemical change may have taken place is fracture formation. A chemical change happens when the substance changes its physical state and composition resulting from a chemical reaction. This chemical reaction may either give off or absorb energy. A change in color is a chemical change. For example, litmus paper turns to red when placed in an acid solution. Production of gas is a chemical change. For example, adding hydrochloric acid to the tiles of the bathroom gives a hissing sound with gases given off. Formation of a precipitate is also a chemical change. Change in shape is not a chemical change.

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3 0

3 years ago

Read 2 more answers

Manganese commonly occurs in nature as a mineral. The extraction of manganese from the carbonite mineral rhodochrosite, involves

hjlf

This is an incomplete question, here is a complete question.

Manganese commonly occurs in nature as a mineral. The extraction of manganese from the carbonite mineral rhodochrosite, involves a two-step process. In the first step, manganese (II) carbonate and oxygen react to form manganese (IV) oxide and carbon dioxide:

$2MnCO_3(s)+O_2(g)\rightarrow 2MnO_2(s)+2CO_2(g)$

In the second step, manganese (IV) oxide and aluminum react to form manganese and aluminum oxide:

$3MnO_2(s)+4Al(s)\rightarrow 3Mn(s)+2Al_2O_3(s)$

Write the net chemical equation for the production of manganese from manganese (II) carbonate, oxygen and aluminum. Be sure your equation is balanced.

Answer : The net chemical equation for the production of manganese is:

$6MnCO_3(s)+3O_2(g)+8Al(s)\rightarrow 6CO_2(g)+6Mn(s)+4Al_2O_3(s)$

Explanation :

The given two chemical reactions are:

(1) $2MnCO_3(s)+O_2(g)\rightarrow 2MnO_2(s)+2CO_2(g)$

(2) $3MnO_2(s)+4Al(s)\rightarrow 3Mn(s)+2Al_2O_3(s)$

First we are multiplying reaction 1 by 3, and reaction 2 by 2, we get:

(1)

(2) $6MnO_2(s)+8Al(s)\rightarrow 6Mn(s)+4Al_2O_3(s)$

Now we are adding both the reactions, we get the overall chemical reaction.

$6MnCO_3(s)+3O_2(g)+6MnO_2(s)+8Al(s)\rightarrow 6MnO_2(s)+6CO_2(g)+6Mn(s)+4Al_2O_3(s)$

The $MnO_2$ is common on both side, by cancelling it, we get:

The net chemical equation for the production of manganese is:

$6MnCO_3(s)+3O_2(g)+8Al(s)\rightarrow 6CO_2(g)+6Mn(s)+4Al_2O_3(s)$

5 0

4 years ago