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spayn [35]
2 years ago
7

What is the atomic number for an element whose mass number is 78,

Chemistry
2 answers:
Ann [662]2 years ago
5 0

Answer:

protons = atomic numbermass number = protons + neutronsatomic number = mass number - neutrons = 78-38 = 40

Explanation:

murzikaleks [220]2 years ago
4 0

Answer:

48

Explanation:

i took the test lolll

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What is the mass of 22.4 L of H2O at STP?
Andrew [12]
Answer is: <span>A. 18.02 g/mol.

At standard temperature and pressure 1 mol of gas occupied 22.4 liters:
V(H</span>₂O) = 22.4 L; volume of water.
Vm = 22.4 L/mol; molar volume at STP.
n(H₂O) = V ÷ Vm.
n(H₂O) = 22.4 L ÷ 22.4 L/mol.
n(H₂O) = 1 mol; amount of substance (water).
M(H₂O) = Ar(O) + 2Ar(H) · g/mol.
M(H₂O) = 16 + 2 ·1.01 · g/mol.
M(H₂O) = 18.02 g/mol; molar mass of water.
3 0
3 years ago
Based on your knowledge of factors that affect the rates of chemical reactions, predict the trend in the last column of the expe
Vinvika [58]

Answer:

See explanation

Explanation:

The rate of reaction depends on on the concentration of reactants. As the concentration of reactants increases, the rate of reaction increases likewise.

If we look at the table, we will discover that the concentration of the thiosulphate is increasing because the volume of water added is decreasing. As such, the rate of reaction increases simultaneously.

Since the rate of reaction increases, the time taken for the cross to disappear decreases steadily. Hence, the values in the last column of the table decreases steadily.

8 0
3 years ago
Loam is a soil texture that is composed of what
finlep [7]
Loam<span> is </span>soil composed<span> mostly of sand (particle size > 63 µm), silt (particle size > 2 µm), and a smaller amount of clay (particle size < 2 µm)</span>
6 0
4 years ago
When a 0.680 g sample of olive oil is burned in a calorimeter, the heat released increases the temperature of 370 g of water fro
Lena [83]

Answer:

the energy value of the olive oil kJ/g = 36.880 KJ/g

Explanation:

we can calculate energy gained by the water which generated by the reaction from this formula :

Q = mc∆t

where:

m is the mass of water= 370 g

c specific heat of water = 4.184 J/g·°C  

∆t is the change or difference in temperature in °C = 38.9 - 22.7 = 16.2 °C

by substitution:

Q = 370g * 4.184 J/g.°C* 16.2°C

   = 25078.896 Joule

the energy value of the olive oil = Q / mass of olive oil

                                                     = 25078.896 Joule/ 0.68 g

                                                     =36880 J/g

                                                      = 36880 / 1000 = 36.880 KJ/g

6 0
3 years ago
Indicate which reaction will occur faster. Explain your reasoning. Select the single best answer. Hexyl chloride or cyclohexyl c
Maslowich

The question is incomplete, the complete question is;

Indicate which reaction will occur faster. Explain your reasoning. Select the single best answer Hexyl chloride or cyclohexyl chloride with sodium azide in aqueous ethanol O Cyclohexyl chloride reacts faster because it is more soluble in the solvent OHexyl chloride reacts faster because it is less sterically hindered. O Cyclohexyl chloride reacts faster because its carbocation intermediate is more stable. Hexyl chloride reacts faster because hydrogen abstraction is more likely to occur in this compound.

Answer:

Hexyl chloride reacts faster because it is less sterically hindered.

Explanation:

Now we have to think through the problem carefully. We must remember that the azide ion is a good nucleophile. Being a good nucleophile, we should be thinking about an SN2 reaction mechanism.

Though ethanol is a polar protic solvent which may weaken the nucleophile by hydrogen bonding, the nucleophile will still react very fast with a primary alkyl halide such as hexyl chloride via SN2 mechanism.

The substrate is easily accessible to the azide ion in hexyl chloride compared to cyclohexyl chloride hence hexyl chloride reacts faster than cyclohexyl chloride.

4 0
3 years ago
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