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adelina 88 [10]

3 years ago

9

Which of the following is true about chemical reactions. A. they are accompanied by changes in energy. B. they form new substanc

es with new properties. C. both A & B
D.neither A nor B

1 answer:

Ilia_Sergeevich [38]3 years ago

7 0

The correct answer should be option C. hope this helps

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A compound is formed when 12.2 g Mg combines completely with 5.16 g N. What is the percent composition of this compound? Please

STALIN [3.7K]

3Mg + N₂= Mg₃N₂
n(Mg)=12,2g÷<span>24,4g/mol=0,5mol-limiting reagent
</span>n(N₂)=5,16g÷28g/mol=0,18mol
n(Mg₃N₂):n(Mg)=1:3, n(Mg₃N₂)=0,166mol, m(Mg₃N₂)=0,166·101,2=16,8g.
%(N)= 2·Ar(N)÷Mr(Mg₃N₂) = 2·14÷101,2=27,66%=0,2766
%(Mg) = 3·Ar(Mg)÷Mr(Mg₃N₂)= 3·24,4÷101,2=72,34% or 100% - 27,66%= 72,34%.

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If 25.5g of sodium thiosulphate was dissolved in 40g of distilled water at 25°C,

zhenek [66]

Answer:

Formula: Na2S2O3

we get solubility.

Divide the mass of the compound by the mass of the solvent and then multiply by 100 g to calculate the solubility in g/100g .

Solution given:

mass of sodium thiosulphate [m1]=25.5g

mass of water [m2]=40g

at temperature [t]=25°C

we have

<u>solubility in g/dm^3</u> : $\frac{solute in gram}{solvent in gram} *100$

= $\frac{25.5}{40}*100$
=63.75g /litre=63.75g/dm³

<u>solubility in g/dm^3 :63.75g/dm³</u>

<u>n</u><u>o</u><u>w</u>

solubility of the solute in mol/dm^3=:63.75g/dm³/178=0.4 mol/dm³

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