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jok3333 [9.3K]
3 years ago
5

Which two elements make up more than 90 of the dry weight of plants?

Chemistry
1 answer:
Temka [501]3 years ago
5 0
The elements are oxygen and carbon
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resistor has a resistance of 1.8 W. How much current passes through the resistor if there is a potential difference of 3.0 V acr
valentinak56 [21]

Answer:

4.0 V?

Explanation

3 0
3 years ago
Match the following associations. Exothermic or endothermic
Alekssandra [29.7K]

<u>Answer:</u>

<em>1) ∆H is positive \Rightarrow Endothermic </em>

<em>2) E_p>E_r \Rightarrow Endothermic  </em>

<em>3) Energy is absorbed \Rightarrow Endothermic </em>

<em>4) E_r>E_p \Rightarrow Exothermic </em>

<em>5) ∆H is negtive \Rightarrow Exothermic </em>

<em></em>

<u>Explanation:</u>

∆H is called as enthalpy change  

It is also called as Heat of reaction

Energy is required for the bond to break a bond.

Energy is released when a bond is formed.

H_2+Cl_2>2HCl

that is

H-H+Cl-Cl>2H-Cl

We see in this equation, bonds between hydrogen and chlorine molecules gets broken and on the right side bond is formed in HCl.

If energy of products greater than energy of reactants then the reaction enthalpy change is endothermic .

If energy of products lesser than energy of reactants then the reaction enthalpy change is exothermic .

For example  

\Delta H=E_p-E_r

=30KJ-20KJ

=+10KJ

(positive hence endothermic)

\Delta H=E_p-E_r

=10KJ-40KJ

=-30KJ

(negative hence exothermic)

8 0
3 years ago
What is the charge on an ion that has an atomic number of 16 and contains 14e-?
lora16 [44]
The answer would be 2+ since the atomic number represents how many protons are in the element. In this case, there are 16 protons, but only 14 electrons, which means there are an additional 2 protons, hence the 2+ charge on the ion.
3 0
2 years ago
4. A student purified a 500-mg sample of phthalic acid by recrystallization from water. The published solubility of phthalic aci
kupik [55]

Answer:

2.77 mL of boiling water is the minimum amount which will dissolve 500 mg of phthalic acid.

Explanation:

We know from the problem that 18 g of phthalic acid are dissolved in 100 mL of water at 99 °C.

Now we devise the following reasoning:

If          18 g of phthalic acid are dissolved in 100 mL of water at 99 °C

Then   0.5 g of phthalic acid are dissolved in X mL of water at 99 °C

X = (0.5 × 100) / 18 = 2.77 mL of water

7 0
3 years ago
Liquid waste that exits the body is _____________ and solid waste is ___________.
nignag [31]

Answer:

The answer is B. Urine, Feces

Explanation:

4 0
2 years ago
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