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siniylev [52]
3 years ago
15

The fossil record is the record of life on earth preserved in rock as fossils. The fossil record provides evidence of what types

of plant and animals lived, how long they lived, how they died, and changed. It also tells us about Earth’s early environment, and how it changed. The fossil record helps determine the age of rock formations by looking at how deep the fossil are buried in the rock. When a fossil is found above another fossil in a rock formation, the deeper fossil are considered older.
What can scientists infer about a specific period of Earth's history if many fossils were discovered from oxygen-breathing organisms?
A) the atmosphere lacked oxygen
B) only fish lived during that time
C) the dinosaurs used all the oxygen
D) the atmosphere had lots of oxygen
Chemistry
2 answers:
Yuki888 [10]3 years ago
5 0

Answer:

the correct answer is d)

Explanation:

strojnjashka [21]3 years ago
3 0

Answer:

d is wrong the correct answer is b

Explanation:

The atmosphere lacked oxygen is correct. The lack of animals that used oxygen suggests that the environment did not have much oxygen.

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What would you use if you needed to determine the density of an object?
Monica [59]
<span>What would you use if you needed to determine the density of an object?

</span>Balance and Graduate Cylinder

Hope This Helps! <span>\(★ω★)/</span>
8 0
3 years ago
For the following problem convert both the reactants to moles and balance chemical equationsThe reaction of 167 g Fe2O3 with 85.
saul85 [17]

Let's start by balancing the reaction:

Fe_2O_3+CO\longrightarrow Fe+CO_2

As we can see, C appears only on two comopunds, CO and CO₂, and since both have 1 C each, their coefficients have to be the same for C to be balanced. However, CO has 1 O and CO₂ has 2, so there is a difference of 1 O betwee them.

The other source of O is Fe₂O₃, that has 3 O. So, we must choose a coefficient for CO and CO₂ such that the difference between the numbers of O is a multiple of 3, that way we can fix this difference with the O from Fe₂O₃. So, we can put coefficients of 3 on both of them:

Fe_2O_3+3CO\longrightarrow Fe+3CO_2

That way, we maintained C balanced (3 on each side) and now we have 3 + 3 O on the left side and 6 O on the right side, so the same amount.

Now, we just have to calance Fe, but it is easy since we have it alone in Fe. Since we have 2 on the left side, it is enough to put a coefficient of 2 on Fe to get the balanced reaction:

Fe_2O_3+3CO\longrightarrow2Fe+3CO_2

Now, to convert from mass to number of moles, we need the molar masses of the reactants, which we can calculate from the atomic weights of the elemnts in each of them:

M_{Fe_2O_3}=2\cdot M_{Fe}+3\cdot M_O=(2\cdot55.845+3\cdot15.9994)g/mol=159.6882g/molM_{CO}=1\cdot M_C+1\cdot M_O=(1\cdot12.0107+1\cdot15.9994)g/mol=28.0101g/mol

Now, we can convert their masses to number of moles:

\begin{gathered} M_{Fe_{2}O_{3}}=\frac{m_{Fe_2O_3}}{n_{Fe_{2}O_{3}}} \\ n_{Fe_2O_3}=\frac{m_{Fe_2O_3}}{M_{Fe_{2}O_{3}}}=\frac{167g}{159.6882g/mol}=1.045787\ldots mol \end{gathered}\begin{gathered} M_{CO}=\frac{m_{CO}}{n_{CO}} \\ n_{CO}=\frac{m_{CO}}{M_{CO}}=\frac{85.8g}{28.0101g/mol}=3.063180\ldots mol \end{gathered}

Now, to determine the limiting reactant, we need to divide both the number of mole by their coefficients on the balanced reaction, so we can see how many we need per reaction of each:

\begin{gathered} Fe_2O_3\colon\frac{n_{Fe_2O_3}}{1}=\frac{1.045787\ldots mol}{1}=1.045787\ldots mol \\ CO\colon\frac{n_{CO}}{3}=\frac{3.063180\ldots mol}{3}=1.021060\ldots mol \end{gathered}

Now, the limiting reactant is the one we have less number of moles per reaction. We can see that we have less CO than Fe₂O₃, so the limiting reactant is CO.

4 0
1 year ago
Approximately how many moles of chlorine make up 1.79 × 1023 atoms of chlorine?
e-lub [12.9K]
1.2*10^24# atoms of chlorine

Explanation:
Chlorine gas (#Cl_2#) has two atoms of elemental chlorine in a molecule, so:
#1# mol of #Cl_2# have #6*10^23# molecules of #Cl_2#
#1# molecule of #Cl_2# have #2# atoms per molucule
Then #2*6*10^23 = 1.2*10^24# atoms of chlorine in a mol of chlorine gas
6 0
3 years ago
The property of metals to be made into wire is called
ANEK [815]

Metal have some properties like lustrous (shiny), good conductors of electricity and heat,etc. Metals have another property by which metal can be drawn into a wire by hammering on it .This property is called as 'ductility'.

hope this helps, please mark brainliest. :)

6 0
2 years ago
What makes physical change a physical change and a chemical change a chemical change
Snowcat [4.5K]
A physical change is any change in a substances form that does not change its chemical makeup. Examples of physical changes are breaking a stick or melting ice. A chemical change occurs when atoms of a substance are rearranged, and the bonds between the atoms are broken or formed. HOPE THIS HELPS!!
6 0
2 years ago
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