Density=mass / volume
Data:
mass=30.0 g
volume=volume with rock - volume without rock=27.6 ml - 22.3 ml=5.3 ml
1 ml=cm³ ⇒ 5.3 ml=5.3 cm³
Therefore:
Density=30.0 g / 5.3 cm³=5.66 g/cm³
Answer: density = 5.66 g/cm³
To find the formulae, you must add as many of the ions together to get a neutral charge. For example, one Li^+ ion and one NO2^- ion give LiNO2, which is lithium nitrite, but since CO3^2- has a charge of -2, it needs 2 Li^+ ions to make the neutral compound Li2CO3, lithium carbonate. Similarly, Cu^2+ needs 2 NO2^- ions to make the neutral compound Cu(NO2)2, copper(II) nitrite. To name these, simply add together the names of the ions used. Li^+ is lithium, Cu^2+ is copper(II), and Ba^2+ is barium. The negatively charged ions are named as nitrite for NO2^-, carbonate for CO3^2-, bisulfate for HSO4^- and phosphate for PO4^3-.
Electrons in sigma <span>bonds remain localized between two atoms. Sigma </span><span>bond results from the formation of </span><span>a molecular orbital </span><span>by the end to </span><span>end overlap of atomic </span>orbitals. Electrons<span> in pi</span> bonds can become delocalized between more than two atoms. Pi bonds result from the formation of molecular orbital by side to side overlap of atomic orbitals.
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1) Answer: A hot pack feels warm when chemicals in it combine.
Explanation: Reactions or process in which heat is released(produced) are known as exothermic reactions or process and those in which the heat is absorbed are known as endothermic reactions or process.
If a beaker feels cools when chemical in it react then it means the chemicals have absorbed the heat energy from its surroundings and so it is an example of an endothermic process.
A hot pack feels warm when chemicals in it combine means the energy is released in the chemical reaction and so it is an example of an exothermic process.
Plants use the sun's energy for photosynthesis which is a process of forming food for the plants. Energy acts as a reactant in this process and so it is an example of endothermic process.
Frying an egg by heating it on a stove is an example of an endothermic process as the heat is required to fry the egg.
So, the only exothermic process is the second one, "A hot pack feels warm when chemicals in it combine."
2) In the given equation, heat is written as a product means the heat is released in the equation and so it is an example of an exothermic reaction.
So, the correct choice is the last one " It is exothermic because energy is released."
Answer:
5.56 × 10^23 molecules
Explanation:
The number of molecules in a molecule can be calculated by multiplying the number of moles in that molecule by Avagadro's number (6.02 × 10^23)
Using mole = mass/molar mass
Molar mass of N2O4 = 14(2) + 16(4)
= 28 + 64
= 92g/mol
mole = 85.0/92
= 0.9239
= 0.924mol
number of molecules of N2O4 (nA) = 0.924 × 6.02 × 10^23
= 5.56 × 10^23 molecules
