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alukav5142 [94]
3 years ago
13

About 25 of the 92 natural elements are known to be essential to life. which four of these 25 elements make up approximately 96%

of living matter? about 25 of the 92 natural elements are known to be essential to life. which four of these 25 elements make up approximately 96% of living matter? carbon, oxygen, phosphorus, hydrogen carbon, hydrogen, nitrogen, oxygen carbon, oxygen, nitrogen, calcium oxygen, hydrogen, calcium, nitrogen carbon, sodium, hydrogen, nitrogen
Chemistry
1 answer:
ikadub [295]3 years ago
6 0
The correct answer would be the second option. Four of these 25 elements that make up approximately 96% of living matter are carbon, hydrogen, nitrogen, oxygen. The elements carbon and hydrogen are the backbone for organic compounds which is the foundation of cells that are present in all living matter. Also, the cells in all living matter are made up of protein which are primarily made up of amino acids which contains nitrogen, oxygen, carbon and hydrogen atoms. So, basically, without these elements in the cells all living matter would not be present and there would be no life in any case.
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When 1.045 g of CaO is added to 50.0 mL of water at 25.0 °C in a calorimeter, the temperature of the water increases to 32.3 °C.
Rus_ich [418]

Answer:

1.71 kJ/mol

Explanation:

The expression for the calculation of the enthalpy change of a process is shown below as:-

\Delta H=m\times C\times \Delta T

Where,  

\Delta H  is the enthalpy change

m is the mass

C is the specific heat capacity

\Delta T  is the temperature change

Thus, given that:-

Mass of CaO = 1.045 g

Specific heat = 4.18 J/g°C

\Delta T=32.3-25.0\ ^0C=7.3\ ^0C

So,  

\Delta H=1.045\times 4.18\times 7.3\ J=31.88713\ J

Also, 1 J = 0.001 kJ

So,  

\Delta H=0.03189\ kJ

Also, Molar mass of CaO = 56.0774 g/mol

Moles=\frac{Mass}{Molar\ mass}=\frac{1.045}{56.0774}\ mol=0.01863\ mol

Thus, Enthalpy change in kJ/mol is:-

\Delta H=\frac{0.03189}{0.01863}\ kJ/mol=1.71\ kJ/mol

8 0
3 years ago
3. A 31.2-g piece of silver (s = 0.237 J/(g · °C)), initially at 277.2°C, is added to 185.8 g of a liquid, initially at 24.4°C,
VARVARA [1.3K]

Answer:

Cp_{liquid}=2.54\frac{J}{g\°C}

Explanation:

Hello,

In this case, since silver is initially hot as it cools down, the heat it loses is gained by the liquid, which can be thermodynamically represented by:

Q_{Ag}=-Q_{liquid}

That in terms of the heat capacities, masses and temperature changes turns out:

m_{Ag}Cp_{Ag}(T_2-T_{Ag})=-m_{liquid}Cp_{liquid}(T_2-T_{liquid})

Since no phase change is happening. Thus, solving for the heat capacity of the liquid we obtain:

Cp_{liquid}=\frac{m_{Ag}Cp_{Ag}(T_2-T_{Ag})}{-m_{liquid}(T_2-T_{liquid})} \\\\Cp_{liquid}=\frac{31.2g*0.237\frac{J}{g\°C}*(28.3-227.2)\°C}{185.8g*(28.3-24.4)\°C}\\ \\Cp_{liquid}=2.54\frac{J}{g\°C}

Best regards.

6 0
4 years ago
A scientist wants to make a solution of tribasic sodium phosphate, Na3PO4, for a laboratory experiment. How many grams of Na3PO4
san4es73 [151]

Answer:

83.20 g of Na3PO4

Explanation:

1 mole of Na3PO4 contains 3 moles of Na+.

Mole of Na ion to be prepared = Molarity x volume

                 = 0.700 x 725/1000

                     = 0.5075 mole

If 1 mole of Na3PO4 contains 3 moles of Na ion, then 0.5075 Na ion will be contained in:

           0.5075/3 x 1 = 0.1692 mole of Na3PO4

mole of Na3PO4 = mass/molar mass = 0.1692

Hence, mass of Na3PO4 = 0.1692 x molar mass

                                     = 0.1692 x 163.94

                                        = 83.20 g.

83.20 g of Na3PO4 will be needed.

3 0
4 years ago
Read 2 more answers
Consider the reaction. 2 Pb ( s ) + O 2 ( g ) ⟶ 2 PbO ( s ) An excess of oxygen reacts with 451.4 g of lead, forming 367.5 g of
Art [367]

Answer : The percent yield of the reaction is, 75.6 %

Solution : Given,

Mass of Pb = 451.4 g

Molar mass of Pb = 207 g/mole

Molar mass of PbO = 223 g/mole

First we have to calculate the moles of Pb.

\text{ Moles of }Pb=\frac{\text{ Mass of }Pb}{\text{ Molar mass of }Pb}=\frac{451.4g}{207g/mole}=2.18moles

Now we have to calculate the moles of PbO

The balanced chemical reaction is,

2Pb(s)+O_2(g)\rightarrow 2PbO(s)

From the reaction, we conclude that

As, 2 mole of Pb react to give 2 mole of PbO

So, 2.18 mole of Pb react to give 2.18 mole of PbO

Now we have to calculate the mass of PbO

\text{ Mass of }PbO=\text{ Moles of }PbO\times \text{ Molar mass of }PbO

\text{ Mass of }PbO=(2.18moles)\times (223g/mole)=486.1g

Theoretical yield of PbO = 486.1 g

Experimental yield of PbO = 367.5 g

Now we have to calculate the percent yield of the reaction.

\% \text{ yield of the reaction}=\frac{\text{ Experimental yield of }PbO}{\text{ Theoretical yield of }PbO}\times 100

\% \text{ yield of the reaction}=\frac{367.5g}{486.1g}\times 100=75.6\%

Therefore, the percent yield of the reaction is, 75.6 %

3 0
4 years ago
Iron has density 7.87 g/cm^3. if 52.4 g of iron is added to 75.0 mL of water in a graduated cylinder, to what volume reading wil
vlada-n [284]

Answer:

6.66 mL

Explanation:

The increase in the volume is due to the addition of the iron whose volume can be calculated as:

Using,

Density = Mass / Volume

Given that:

Density of Iron = 7.87 g/cm³

Mass of iron = 52.4 g

Thus, volume is:

Volume = Mass / Density = 52.4 / 7.87 cm³ = 6.66 cm³

Also, 1 cm³ = 1 mL

<u>The rise in the volume = 6.66 mL</u>

8 0
3 years ago
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