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slamgirl [31]
3 years ago
14

Which geologic time did humans exist​

Chemistry
1 answer:
masha68 [24]3 years ago
8 0

<h2><u>PLEASE MARK BRAINLIEST!</u></h2>

It is believed that, 66 million years ago, the first human lived. This is according to fossil. It is thought that, after the Cretaceous–Paleogene extinction [the extinction of dinosaurs and 3/4 of plant and animal life], the first humans appeared.

I hope this helps!

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Calculate the pOH of this solution. pH = 1.90 pOH =
ladessa [460]

Answer:

<h2>12.1 </h2>

Explanation:

Since the pH has been given, the pOH can be found by using the formula

pH + pOH = 14

pOH = 14 - pH

From the question we have

pOH = 14 - 1.9

We have the final answer as

<h3>12.1</h3>

Hope this helps you

8 0
3 years ago
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What is the concentration of 10.00mL of HBr if it takes 16.73 mL of a 0.253M LiOH solution to neutralize it?
Fudgin [204]
The chemical reaction would be expressed as follows:

HBr + LiOH = LiBr + H2O

We are given the volumes and corresponding concentration to be used for the reaction. We use these values to solve for the concentration of the other reactant. We do as follows:

0.253 mol LiOH / L solution ( 0.01673 L ) ( 1 mol HBr / 1 mol LiOH ) = 0.00423 HBr needed

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3 0
3 years ago
List 4 things that can affect the rate of reaction during a chemical reaction.
laiz [17]

Answer:

Reactant concentration, the physical state of the reactants, and surface area, temperature, and the presence of a catalyst are the four main factors that affect reaction rate.

Explanation:

6 0
3 years ago
Is a pencil a compound or an element and is a pencil heterogeneous or homogeneous
masya89 [10]

Answer:

Pencil is an element and a heterogeneous mixture

Explanation:

6 0
3 years ago
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How many grams of Mg are needed to produce 224 g of MgO in the complete reaction of Mg
zmey [24]

Answer:

134.4 g of Mg

Explanation:

reaction:

2Mg + O2 ➡️ 2MgO

1) find the mol of MgO

mol = mass / molar mass

mass = 224 g

molar mass = 24+16 = 40

mol = 224 / 40

= 5.6 moles

2 mol = 5.6 moles

2) find the mass of Mg

mass = mol × molar mass

mol = 5.6

molar mass = 24

mass = 5.6 × 24

= 134.4 g

7 0
3 years ago
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