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pogonyaev
3 years ago
10

In what eon did single-celled organisms appear?

Chemistry
1 answer:
fomenos3 years ago
4 0
Archean is what I think but there isn’t a clear answer
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The pH of a substance can only be determined when it is
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The pH of a substance can only be determined when it is
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What must happen for heat to be transferred by thermal conduction?
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yh what he said

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What is the most common way atoms combine
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Atoms combine<span> by forming chemical bonds</span>
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In the process of attempting to characterize a substance, a chemist makes the following observations: (a) The substance is a sil
Amiraneli [1.4K]

The question is incomplete, this is the complete question;

In the process of attempting to characterize a substance, a chemist makes the following observations. Which are physical properties and which are chemical properties?

(a) The substance is a silvery white, lustrous metal.

(b) The substance melts at 649 ∘C

(c) The substance boils at 1105 ∘C.

(d) The density of the substance at 20 ∘C is 1.738 g/cm³.

(e) The substance burns in air, producing an intense white light.

(f) The substance reacts with chlorine to give a brittle white solid.

(g) The substance can be pounded into thin sheets or drawn into wires.

(h) The substance is a good conductor of electricity.

Answer:

(a) Physical

(b) Physical

(c) Physical

(d) Physical

(e) Chemical

(f) Chemical

(g) Physical

(h) Physical

Explanation:

(a) The substance is a silvery white, lustrous metal - is appearance which is physical.

(b) The substance melts at 649 ∘C metling point is a physical measurement

(c) The substance boils at 1105 ∘C boiling point is a physical measurement

(d) The density of the substance at 20 ∘C is 1.738 g/cm3 how heavy a substance is,is physical.

(e) The substance burns in air, producing an intense white light. Burning is a chemical change. It is a reaction of a substance with oxygen

(f) The substance reacts with chlorine to give a brittle white solid. This is a chemical reaction as the question says.

(g) The substance can be pounded into thin sheets or drawn into wires. Ductility is a physical change, the substance remains chemically unchanged

(h) The substance is a good conductor of electricity. Any conductivity is physical, the substance remains chemically unchanged

7 0
3 years ago
FIRST ANSWER = BRAINLIEST
STALIN [3.7K]

A_{r} = 24.3

The average atomic mass of X is the <em>weighted average</em> of the atomic masses of its isotopes.  

We multiply the atomic mass of each isotope by a number representing its <em>relative importance</em> (i.e., its % abundance).  

Thus,  

0.790 × 24 u = 18.96 u

0.100 × 25 u =   2.50 u

0.110 × 26 u =    <u>2.86 u</u>  

       TOTAL =  24.3   u

∴ The relative atomic mass of X is 24.3.


5 0
3 years ago
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