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BabaBlast [244]
3 years ago
6

Is it true or false that dry air is 78% nitrogen and 21% carbon dioxide?

Chemistry
1 answer:
Komok [63]3 years ago
5 0
The answer is false, oxygen
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Where are the instructions that tell the cell everything it needs to survive?
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Answer:

Nucleolus

Explanation:

It holds the DNA

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How many mL of a 0.250M sodium hydroxide solution is needed to neutralize 25.0 mL of a 0.430M sulfuric acid solution?
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86.0 mL

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Solutions that are very concentrated have greater freezing point depression Group of answer choices true or false
Tamiku [17]

Answer:

Explanation:

False. The greater the concentration, the lower the freezing point.

8 0
3 years ago
Which of the reactions are exothermic?
Nutka1998 [239]

Answer:

Reaction A, B, E and F are exothermic reactions.

Explanation:

Exothermic reactions are defined as the reactions in which energy of reactants is more than the energy of the products. In these reactions, energy is released by the system.

The total enthalpy of the reaction (\Delta H) comes out to be negative.

Endothermic reactions are defined as the reactions in which energy of products is more than the energy of the reactants. In these reactions, energy is absorbed by the system.

The total enthalpy of the reaction (\Delta H) comes out to be positive.

So, from the given option reaction which are exothermic are with negative value (\Delta H) that enthalpy of reaction and those are:

1) 2Mg(s) + O_2( g )\rightarrow 2MgO (s),ΔH = -1203 kJ/mol

2)NH_3 (g) + HCl (g)\rightarrow NH_4Cl (s),ΔH =-176 kJ/mol

3) C(graphite) + O_2 (g)\rightarrow CO_2 (g),ΔH = -393.5 kJ/mol

4) CH_4 (g) + 2O2 (g)\rightarrow CO_2 (g) + 2H_2O (l),ΔH =-891 kJ/mol

6 0
4 years ago
Q1. Briefly explain why the Zeff experienced by a valence electron in Cl is larger than in Mg. Q2. Briefly explain why the Zeff
Inessa05 [86]

Answer:

See explanation

Explanation:

Q1:

Chlorine has 17 protons while magnesium has only 12 protons. Recall that the Zeff depends on the size of the nuclear charge. The greater the size of the nuclear charge, the larger the Zeff experienced by a valence electron.

Q2:

The larger the Zeff, the smaller the atomic radius. Since the valence electrons of Cl experience a greater Zeff than those of Mg due to greater size of the nuclear charge, the atomic radius of chlorine will be smaller than that of Mg.

Q3:

The radius of an atom increases as the value of the principal quantum number (n) increases down the group due to addition of more shells. The greater the number of shells added, the greater the principal quantum number (n) and the greater the atomic radius, hence the answer.

5 0
3 years ago
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