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asambeis [7]
3 years ago
15

Why didn't scientists know about atoms for a long time

Chemistry
1 answer:
fredd [130]3 years ago
6 0
They didnt have a powerfull enough microscope to see them an when they could they were moving to fast unless they were cold

You might be interested in
A .......... notifies you that danger is present if the directions are not followed.
maksim [4K]

Answer:

A. Warning

Explanation:

Out of all said choices, the best choice would be warning since it would fit the sentence the most.

"A Warning notifies you that danger is present." compared to:

"A Hazard notifies you that danger is present."

"A Safety notifies you that danger is present."

"A Danger notifies you that danger is present."

5 0
2 years ago
Please help me out i don’t get this. what is the answers to 1-4.
VLD [36.1K]

Answer:

1. A circuit is a path that electricity flows along. It starts at a power source, like a battery, and flows through a wire to a light bulb or other object and back to other side of the power source.

2. A series circuit is one that has more than one resistor, but only one path through which the electricity (electrons) flows. All the components in a series circuit are connected end-to-end. A resistor in a circuit is anything that uses some of the power from the cell.

3. A parallel circuit is a circuit in which the electric current passes through two or more branches or connected parts at the same time before it combines again. Compare.

4. BOTH - 1. lightbulb 2. battery 3. switch

   SERIES- 1. Ammeter 2. voltmeter

i'm not sure about the rest sorry :(

7 0
3 years ago
a culinary student fills a 40ml container with 37.2 grams of vegetable oil.What is the density of the oil
Lynna [10]

Answer:

<h2>0.93 g/mL</h2>

Explanation:

The density of a substance can be found by using the formula

density =  \frac{mass}{volume} \\

From the question

mass = 37.2 g

volume = 40 mL

We have

density =  \frac{37.2}{40}  \\  = 0.93

We have the final answer as

<h3>0.93 g/mL</h3>

Hope this helps you

4 0
2 years ago
How many milliliters of a 0.285 M HCl solution are needed to neutralize 249 mL of a 0.0443 M Ba(OH)2 solution?
meriva

Answer:

\large \boxed{\text{77.4 mL}}

Explanation:

                Ba(OH)₂ + 2HCl ⟶ BaCl₂ + H₂O

    V/mL:     249

c/mol·L⁻¹:  0.0443     0.285

1. Calculate the moles of Ba(OH)₂

\text{Moles of Ba(OH)$_{2}$} = \text{0.249 L Ba(OH)}_{2} \times \dfrac{\text{0.0443 mol Ba(OH)}_{2}}{\text{1 L Ba(OH)$_{2}$}} = \text{0.011 03 mol Ba(OH)}_{2}

2. Calculate the moles of HCl

The molar ratio is 2 mol HCl:1 mol Ba(OH)₂

\text{Moles of HCl} = \text{0.011 03 mol Ba(OH)}_{2} \times \dfrac{\text{2 mol HCl}}{\text{1  mol Ba(OH)}_{2}} = \text{0.022 06 mol HCl}

3. Calculate the volume of HCl

V_{\text{HCl}} = \text{0.022 06 mol HCl} \times \dfrac{\text{1 L HCl}}{\text{0.285 mol HCl}} = \text{0.0774 L HCl} = \textbf{77.4 mL HCl}\\\\\text{You must add $\large \boxed{\textbf{77.4 mL}}$ of HCl.}

8 0
3 years ago
Which of the following processes are exothermic?Which of the following processes are exothermic?Br(g) + e- → Br-(g)Li(s) → Li(g)
Ksenya-84 [330]

Answer:

The correct answer is:  None of the above are exothermic.

Explanation:

Energy is the ability to perform a job or to produce heat. Chemical reactions involve a rearrangement of atoms between substances with rupture or formation of chemical bonds and this generates changes in the energy of the system.

An exothermic reaction is that reaction where heat is released. This means that the energy of the molecules of the products is less than the energy of the molecules of the reactants.

An endothermic reaction is that chemical reaction that, when it occurs, consumes energy, that is, the products obtained have greater energy than the initial reagents, since they have taken part of the heat of the environment.

Sublimation is the change of state of a substance from solid to gas directly without going through the liquid state. This process requires energy to be carried out because the strong attractive energies between the solid molecules must be broken. So it is an endothermic process. This is what happens in the following reactions:

Li(s) → Li(g)

NaF(s) → Na+(g) + F-(g)

Dissociation is a process in which complexes, molecules or salts are separated into smaller molecules, ions or radicals, usually reversibly. Within the dissociation is the homolytic rupture, where each atom separates and carries the same charge of electrons. Thus free radicals are formed. To dissociate or break these bonds requires energy, so it is endothermic. This type of reaction occurs in:

Cl2(g) → 2Cl(g)

Electronic affinity is defined as the energy exchanged when an isolated and fundamental state gaseous atom takes an electron to form an anion (negative ion).  When the electronic affinity is greater than zero, the process would be endothermic and when the electroaffinity is less than zero, the process would be exothermic.

This occurs in:

Br(g) + e- → Br-(g)

The highest electronic affinities are for the elements of group 17 of the periodic table, the group to which bromine belongs. This means that the electronic affinity is greater than zero and is endothermic.

<u><em>The correct answer is:  None of the above are exothermic.</em></u>

<u><em>Br(g) + e- → Br-(g) </em></u>

7 0
3 years ago
Read 2 more answers
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