What happens in a chemical change that does not occur in a physical change?

Chemistry

1 answer:

Andrej [43]3 years ago

6 0

Answer:

In a chemical reaction, there is a change in the composition of the substances in question; in a physical change there is a difference in the appearance, smell, or simple display of a sample of matter without a change in composition. Although we call them physical "reactions," no reaction is actually occurring.

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The density of ethanol is 0.789 g/cm^3 at 20 degrees C. What volume of ethanol has a mass of 15.5 grams?

lys-0071 [83]

<span>density = mass / volume

given the quotient , we have density and mass, volume can be easily calculated as:

volume = mass / p =15.5 g / 0.789 g/cm^3

=~ 20 cm^3 (dimension ally constant)</span>

6 0

3 years ago

Use the IUPAC nomenclature rules to give the name for Mg(ClO4)2

Makovka662 [10]

Answer:

The answer to your question is Magnesium Perchlorate

Explanation:

IUPAC Rules to name ternary salts of chlorine

1.- Ternary salts use prefixes and suffixes it depends on the number of oxygens they have.

Example

Metal + Chlorine + 1 oxygen = Name of the metal + hipo chlor + ite

Metal + Chlorine + 2 oxygens = Name of the metal + chlor + ite

Metal + Chlorine + 3 oxygens = Name of the metal + chlor + ate

Metal + Chlorine + 4 oxygens = Name of the metal + per + chlor + ate

For this compound the name is Magnesium Perchlorate.

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2 years ago

Find the number of moles in 3.62 x 1024 atoms of helium.

Makovka662 [10]

3.62x10^24/ 6.02x10^23= 6.013 moles to 3dp

8 0

3 years ago

Read 2 more answers

Calculate the standard reaction enthalpy for the reaction NO2(g) → NO(g) + O(g) given +142.7 kJ/mol for the standard enthalpy of

bulgar [2K]

Answer:

The standard reaction enthalpy for the given reaction is 235.15 kJ/mol.

Explanation:

$O_2(g) \rightarrow \frac{2}{3}O_3(g),\Delta H^o_{1}=142.7 kJ/mol$ ..[1]

$O_2(g) \rightarrow 2 O(g),\Delta H^o_{2}=498.4 kJ/mol$ ..[2]

$NO(g) + O_3(g)\rightarrow NO_2(g) + O_2(g) ,\Delta H^o_{3} = -200 kJ/mol$ ..[3]

$NO_2(g)\rightarrow NO(g) + O(g),\Delta H^o_{4}=?$ ..[4]

Using Hess's law:

Hess’s law of constant heat summation states that the amount of heat absorbed or evolved in a given chemical equation remains the same whether the process occurs in one step or several steps.

2 × [4] = [2]- (3 ) × [1] - (2) × [3]

$2\times \Delta H^o_{4}=\Delta H^o_{2} -3\times \Delta H^o_{1}-2\times \Delta H^o_{3}$