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tino4ka555 [31]
3 years ago
8

Which of these substances are elements?

Chemistry
2 answers:
Aleks04 [339]3 years ago
8 0
An element is a species of atom that has the same amounts of electrons and protons in their nuclei. To know which of these substances are elements, we can look it up in the periodic table of elements. The elements are as follows:

1.silicon
2.lead
3.silicone
5.iodine

Andru [333]3 years ago
8 0

Answer is:

1. silicon.

2. lead.

5. iodine.

Silicon (symbol: Si) is an element with atomic number 14 (14 protons).

Lead (Pb) is an element with atomic number 82.

Iodine (I) is an element with atomic number 53.

Silicone is a compound (polymer) made of silicon, oxygen, hydrogen, carbon and other elements.

Quartz is a compound (mineral) made of silicon and oxygen atoms.

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The reaction P4 +502P4010 + 712 kcal is
igor_vitrenko [27]

Answer:

The reaction is exothermic (option 4)

Explanation:

P4 + 5O2 → P4O10 + 712 kcal

In chemical reactions heat can be absorbed or released:

⇒in the first case, when heat is absorbed, this is called an endothermic reaction. The products have more energy than the reactants. The reaction requires or absorbs energy from it's surroundings.  That means  that in this reaction energy , in the form of heat, will be absorbed by the reactants.

⇒ when heat is released, this is called an exothermic reaction. The reactants have more energy than the products. The reaction gives or releases energy to it's surroundings.  That means  that in this reaction energy , in the form of heat, will be released by the reactants.

in the case of P4 + 5O2 → P4O10 + 712 kcal

We notice that on the right side, which is the product side, there is a positive amount of energy. This means that the energy is released by the the reactants, in this reaction. <u>The reaction is exothermic.</u>

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4 0
2 years ago
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What are some examples of how matter moves through a cycle on earth ​
olganol [36]

Answer:

Ocean, lakes and rivers. Are all liquids.

Explanation:

Ocean, lakes and rivers. Are all liquids. Snow starts off as a liquid, evaporates into a gas and camoes back as snow.

4 0
3 years ago
In science, we like to develop explanations that we can use to predict the outcome of events and phenomena. Try to develop an ex
Kay [80]

The question is incomplete. The complete question is :

In science, we like to develop explanations that we can use to predict the outcome of events and phenomena. Try to develop an explanation that tells how much NaOH needs to be added to a beaker of HCl to cause the color to change. Your explanation can be something like: The color change will occur when [some amount] of NaOH is added because the color change occurs when [some condition]. The goal for your explanation is that it describes the outcome of this example, but can also be used to predict the outcome of other examples of this phenomenon. Here's an example explanation: The color of the solution will change when 40 ml of NaOH is added to a beaker of HCl because the color always changes when 40ml of base is added. Although this explanation works for this example, it probably won't work in examples where the flask contains a different amount of HCl, such as 30ml. Try to make an explanation that accurately predicts the outcome of other versions of this phenomenon.

Solution :

Consider the equation of the reaction between NaOH and $HCl$

  NaOH (aq) + HCl (aq) → NaCl(aq) + $H_2O (l)$

The above equation tells us that $1 \text{mole}$ of $NaOH$ reacts with $1 \text{mole}$ of $HCl$.

So at the equivalence point, the moles of NaOH added = moles of $HCl$present.

If the volume of the $HCl$ taken = $V_1$ mL and the conc. of $HCl$ = $M_1$  mole/L

The volume of NaOH added up to the color change = $V_2 \text{  and conc of NaOH = M}_2$ mole/L

Moles of $HCl$ taken = $V_1 \ mL \times M_1 \ mol/100 \ mL = V_2M_2 \times 10^{-3}$  moles.

The color change will occur when the moles of NaOH added is equal to the moles of $HCl$ taken.

Thus when $V_1 M_1 \times 10^{-3} = V_2M_2 \times 10^{-3}$

or   when    $V_1M_1 = V_2M_2$

or $V_2=\frac{V_1M_1}{M_2}$  mL of NaOH added, we observe the color change.

Where $V_1, M_1$ are the volume and molarity of the $HCl$ taken.

$M_2$ is the molarity of NaOH added.

When both the NaOH and $HCl$ are of the same concentrations, i.e. if $M_1=M_2$, then $V_2=V_1$

Or the 40 mL of $HCl$ will need 40 mL of NaOH for a color change and

30 mL of $HCl$ would need 30 mL of NaOH for the color change (provided the concentration $M_1=M_2$)

7 0
2 years ago
An electron:
Korvikt [17]
It has a negative charge emits energy when it moves to a lower energy orbit from an excited state and it has the same mass as a proton
4 0
3 years ago
A meteor falls toward Earth's surface. Given that the acceleration due to
ICE Princess25 [194]

Answer:

E = 147000  J

Explanation:

Given that,

The mass of meteor, m = 50 kg

The altitude of the meteor, h = 300 m

We need to find the potential energy of the meteor. The formula for the potential energy is given by :

E=mgh

Put all the values,

E=50\times 9.8\times 300\\\\E=147000\ J

So, the required potential energy is equal to 147000  J.

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3 years ago
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