Answer:
A. 2 chlorine (Cl) atoms
Explanation:
2 chlorine atoms means that chlorine is a gas.
Sodium (Na) reacts with 2 chlorine atoms according to the equation below;
Na(s) + Cl2(g) => NaCl2
Answer:
Filtration is a method for separating an insoluble solid from a liquid. When a mixture of sand and water is filtered: the sand stays behind in the filter paper (it becomes the residue ) the water passes through the filter paper (it becomes the filtrate )
Explanation:
Answer:
- <em>The substance that cannot be broken down by a chemical change is </em><u>tungsten (option C)</u>
Explanation:
Chemical compounds are pure <em>substances</em> constituted by two or more different elements. They have fixed composition and have their unique chemical properties, different from their individual components (elements) and from other compounds.
Thus chemical compounds can<em> be broken down by a chemical change</em> into their individual atoms or other simpler compounds.
The substances indicated by the choices <em>A) methane, B) propanal, and D) water</em>, are chemical compounds with chemical formulae CH₄, C₃H₆O, and H₂O, respectively, so they<em> can be broken down into their consitutents by a chemical change</em>.
On the other hand, <em>tungsten</em> is one of the 118 known elements. Its atomic number is 74, and its chemical symbol is W.
Then, being tungsten an element, which means that all the atoms present in a pure sample have the same number of protons and electrons, it <em>cannot be broken down by a chemical change</em>. The only way to split an atom of tungsten is by a nuclear reaction.
<h2>Which of the following reactions is endothermic-</h2><h2>½N2(g) + O2(g) + 8.1 kcal → NO2(g)</h2>
Explanation:
Chemical reaction
When two or more substances react and form some new substance it is called as chemical reaction .
A + B --> C + D
(reactants ) (products )
When ever chemical reaction occurs following changes can occur :
- Change in colour
- Ppt formation
- energy changes
- Change in state
- Evolution of gas etc
On the basis of energy changes : reactions are of two types :
Endothermic
Exothermic
Endothermic reaction
A reaction in which heat is absorbed .
Example :½N2(g) + O2(g) + 8.1 kcal → NO2(g)
Exothermic reaction
A reaction in which heat is released .
For example : H2(g) + ½O2(g) → H2O(g), ΔH = -57.82 kcal
½N2(g) + 3/2H2(g) → NH3(g) + 11.0 kcal
C(diamond) + O2(g) → CO2, ΔH = -94.50 kcal
Answer:
b. The nitrogen atom shares one valence electron with each iodine atom, which also shares one valence electron each with the nitrogen atom.
Explanation:
The formula of nitrogen triiodide is NI3. In this compound, the nitrogen atom shares one valence electron with each chlorine atom which in turn also shares a valence electron with nitrogen.
Recall that covalent bonding involves a sharing of <u>valence </u> electrons. Transfer of electrons is typical of ionic bonds between a metal and a nonmetal. nitrogen and iodine are nonmetals hence they bond covalently.
Hence, the formation of NI3 leaves three lone pairs on each chlorine atom and one lone pair on the nitrogen atom.