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3 years ago

Fossil A is found in a rock layer above a layer containing Fossil B. Which fossil is probably older?

Chemistry

1 answer:

ch4aika [34]3 years ago

4 0

Answer:

Fossil B

Explanation:

Fossil B is older because it's later is at the bottom

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The useful metal manganese can be extracted from the mineral rhodochrosite by a two-step process.... In the first step, manganes

frez [133]

Answer : The mass of $MnCO_3$ required are, 35 kg

Explanation :

First we have to calculate the mass of $MnO_2$ .

The first step balanced chemical reaction is:

$2MnCO_3+O_2\rightarrow 2MnO_2+2CO_2$

Molar mass of $MnCO_3$ = 115 g/mole

Molar mass of $MnO_2$ = 87 g/mole

Let the mass of $MnCO_3$ be, 'x' grams.

From the balanced reaction, we conclude that

As, $(2\times 115)g$ of $MnCO_3$ react to give $(2\times 87)g$ of $MnO_2$

So, $xg$ of $MnCO_3$ react to give $\frac{(2\times 87)g}{(2\times 115)g}\times x=0.757xg$ of $MnO_2$

And as we are given that the yield produced from the first step is, 65 % that means,

$60\% \text{ of }0.757xg=\frac{60}{100}\times 0.757x=0.4542xg$

The mass of $MnO_2$ obtained = 0.4542x g

Now we have to calculate the mass of $Mn$ .

The second step balanced chemical reaction is:

$3MnO_2+4Al\rightarrow 3Mn+2Al_2O_3$

Molar mass of $MnO_2$ = 87 g/mole

Molar mass of $Mn$ = 55 g/mole

From the balanced reaction, we conclude that

As, $(3\times 87)g$ of $MnO_2$ react to give $(3\times 55)g$ of $Mn$

So, $0.4542xg$ of $MnO_2$ react to give $\frac{(3\times 55)g}{(3\times 87)g}\times 0.4542x=0.287xg$ of $Mn$

And as we are given that the yield produced from the second step is, 80 % that means,

$80\% \text{ of }0.287xg=\frac{80}{100}\times 0.287x=0.2296xg$

The mass of $Mn$ obtained = 0.2296x g

The given mass of Mn = 8.0 kg = 8000 g (1 kg = 1000 g)

So, 0.2296x = 8000

x = 34843.20 g = 34.84 kg = 35 kg

Therefore, the mass of $MnCO_3$ required are, 35 kg

4 0

3 years ago

Read 2 more answers

How do elements differ going from left to right across a period on the periodic table?

Nuetrik [128]

Their atomic number increases

6 0

3 years ago

1- Science that deals with the identification and quantification of the components of material systems

Elis [28]

Answer:

Analytical science

Explanation:

7 0

4 years ago

You need 455 ml of a 75% alcohol solution. on hand, you have a 25% alcohol mixture. you also have a 90% alcohol mixture. how muc

marishachu [46]

X ml - <span>25% alcohol mixture
y ml - </span><span>90% alcohol mixture

x+y = 455

0.25x ml alcohol in </span>x ml of 25% alcohol mixture
0.9y ml alcohol in y ml of  90% alcohol mixture
0.75*455= 341.25 ml alcohol in 455 ml of  75% alcohol mixture

0.25x+0.9y=341.25

System of equations:

x+y = 455 /*(-0.25) ------> -0.25x-0.25y = -0.25*455
0.25x+0.9y=341.25

-0.25x-0.25y=-113.75
0.25x+0.9y=341.25 Add both equations

0.25x+0.9y-0.25x-0.25y=341.25-113.75
0.65y =227.5
y=227.5/0.65 = 350 ml  of  90% alcohol mixture

x+y=455
x+355=455
x=100 ml of  25% alcohol mixture

8 0

3 years ago

Give the number of covalent bonds that a carbon atom can form.

polet [3.4K]

Answer:

four covalent bonds

Explanation:

A carbon atom would form 4 covalent bonds.

For a covalent bond to be formed, an atom would share its valence electrons with another. In this process, each atom would require unpaired electrons for this bond to be formed. The number of available unpaired electrons would represent the number of electrons needed to complete the outer energy level of the atom.

In a carbon atom, we have no lone pair of electrons and 4 unpaired electrons. When these 4 electrons are shared with those of other atoms, they produce a complete octet which perfectly mimics the noble gases.

3 0

3 years ago