Answer:
45.2%
Explanation:
To calculate the percent of an element in a compound we divide the molar mass of the element by the compound and multiply that by 100
First lets find the molar mass of Fluoride
Looking at the periodic table Fluoride has a molecular mass of 18.998 g
Now we need to find the molecular mass of NaF
Looking at a periodic table, Sodium (Na) has a molecular mass of 22.990g and Fluoride has a molecular mass of 18.998 so NaF has a molecular mass of 22.990(1) + 18.998(1) = 41.988g
Now we divide the mass of fluoride by the mass of sodium fluoride and multiply that by 100 to find the percentage of fluoride that is present in NaF
Mass of Fluoride = 18.998g
Mass of Sodium Fluoride = 41.988g
Percentage of fluoride present in NaF = (18.998g / 41.988g) * 100 = 45.2%
Answer:
The compound is N2O4
Explanation:
We have certain important pieces of information about the compound;
1) it is an oxide (a binary compound of nitrogen and oxygen)
2) there are no N-N bonds present
3) there are no O-O bonds present
Since it contains only nitrogen and oxygen then nitrogen accounts for 25.9% of the molecule by mass then oxygen should account for (100-25.9) = 74.1% oxygen
Relative atomic mass of oxygen = 16
Relative atomic mass of nitrogen = 14
We now deduce the empirical formula
Nitrogen. Oxygen
25.9/14. 74.1/16
1.85/1.85. 4.6/1.85 (divide through by the lowest ratio)
1 2
Empirical formula is NO2
To find the molecular formula
(NO2)n = 108
(14+2(16))n= 108
46n=108
n= 108/46
n= 2
Therefore molecular formula= N2O4
24. <span>Valence electrons are most loosely held by the atom and are involved in chemical reactions. Chemical reactions occur when valence electrons are shared between atoms. The number of valence electrons determines how these reactions take place and what kind of bonds they form.
25 </span><span>Sodium has one valence electron and chlorine has seven valence electrons. The Ione valence electron from sodium is lost and is transferred to the chlorine atom. The result is a sodium ion with a charge of 1+ and a chloride ion with a charge of 1-. The oppositely charged ions attract each other and the charges balance to make a compound that is electrically neutral.
26. </span><span>Ionic compounds have high melting points and high boiling points compared to molecular compounds. Ionic compounds that are dissolved in water or melted will conduct electricity. Molecular compounds do not conduct electricity in either case.
27. </span><span>A covalent bond is formed when two atoms share valence electrons. Neither atom loses electrons or takes electrons from the other. No charged particles form. In an ionic bond, one or more electrons are transferred from one atom to another. Atoms that lose electrons become positively charged ions, and atoms that gain electrons become negatively charged ions. These oppositely charged particles then attract each other.
28. </span><span>A metal crystal consists of positively charged metal ions embedded in a "sea" of loosely held valence electrons that can move around easily. Heat travels through materials as the increased motion of the particles in the hotter parts of the material is passed along to the particles in the cooler parts. In a metal, since particles are easily set in motion, heat is easily transferred or conducted. The same is true for the conduction of electricity. Electricity can flow when charged particles, such as electrons, are free to move. Since the electrons in a metal crystal can move freely among the atoms, electricity is easily conducted.</span>
10. Capital C and D represent products of chemical reaction, the capital A and B represent reactants, <span>the lower case letter represent coefficients (how many atoms or molecules in chemical reaction).
12. According to </span><span>Le </span>Chatelier's principle (if<span> the concentration is changed, that will shift the equilibrium to the side that would reduce that change in concentration)</span> <span>the equilibrium shift to the left.
13. </span>According to Le Chatelier's principle the equilibrium shift to the right.
14. According to Le Chatelier's principle (<span>When the reaction is </span>exothermic<span>, heat is included as a product)</span> the equilibrium shift to the right.
