What are the most elements of the periodic table?

The atomic mass of boron is 10.811. What is the mass number of the most

Sati [7]

Answer:

C.11

Explanation:

Boron-11 makes up around 80% of all natural Boron. And, typically, the quickest way to determine the most abundant isotope of an element is to just round the atomic mass to the nearest whole number.

7 0

3 years ago

Research is being carried out on cellulose as a source of chemicals for the production of fibers, coatings, and plastics. Cellul

Luden [163]

Answer:

+ 636 KJ

Explanation:

We want to arrive to the equation

C6H12O6(s) ---------> 6 H2CO(g) ΔH ° rxn = ?

by manipulating algebraically the first four given equations.

We notice the first one has our product H2CO(g) as a reactant. This indicates we must take the inverse of that equation. Also we need 6 mol of H2CO(g), thus it also needs to be multiplied by 6

6 CO2(g) + 6 H2O(g) ------->6H2CO(g) + 6O2(g) ΔH °comb = + 572.9 KJ/x 6

Now we want C6H12O6(s) as a reactant and it is a product in the second one, therefore lets reverse it

C6H12O6(s) -------> 6 C(s) + 6 H2(g) + 3 O2(g) ΔH ° f = + 1274.4 KJ/mol

Now if take the third equation and multiply it by six we will cancel the C(s) with the above equation

6 C(s) + 6O2(g) ---------> 6 CO2(g) ΔH ° f = - 393.5 KJ/mol x 6

Finally by multiplying the last equation by 6 and adding all the equations we will arrive at our desired one

6 H2(g) + 3 O2(g) -----------> 6H2O(g) ΔH ° f = - 285.8 KJ/mol x 6

then lets add them to get ΔH ° rxn:

6 CO2(g) + 6 H2O(g) ------->6H2CO(g) + 6O2(g) ΔH °comb = + 3437.4 KJ

+ C6H12O6(s) -------> 6 C(s) + 6 H2(g) + 3 O2(g) ΔH ° f = + 1274.4 KJ

+ 6C(s) + 6O2(g) ---------> 6 CO2(g) ΔH ° f = - 2361.0 KJ

+6 H2(g) + 3 O2(g) -----------> 6H2O(g) ΔHº f = - 1714.8 KJ

C6H12O6(s) ---------> 6 H2CO(g)

ΔH ° rxn = 3437.4 + 1274.4 - 2361.0 - 1714.8 = 636 KJ

8 0

3 years ago

A 58.0mL sample of a 0.122M potassium sulfate solution is mixed with 40.0mL of a 0.102M Lead(II) acetate solution and this preci

vlada-n [284]

First we need to find the limiting reactant. This is the reactant that is theoretically consumed completely first. Theoretical yield is how much product is produced given the limiting reactant is consumed and the percent yield is the fraction of the actual products produced and the theoretical products produced.

The limiting reactant is Pb(C2H3O2)2.
The theoretical yield is 1.2373008g and you should get the Percent yield which is Actual yield/theoretical yield.

7 0

3 years ago

Read 2 more answers

Which statement is true about the ionic size of the elements in a group as one moves from top to bottom in that group?

nekit [7.7K]

Answer:

Ionic size increases from top to bottom within the group.

Explanation:

Ions are formed when neutral atoms of elements gain or lose electron(s).
The ionic radius is the distance from the nucleus of an ion to the outermost energy level.
The ionic size or radius increases down the group as the number of energy level increases.
Therefore, an ion of an element lower in the group will be larger than the ion of an element higher in the group.
For example, an ion of potassium, K+, is larger in size compared to the ion of sodium, Na+ since K+ has more energy levels than Na+.

8 0

3 years ago

Read 2 more answers

Consider the following equilibrium:H2CO3(aq) + H2O(l) H3O+(aq) + HCO3-1(aq).What is the correct equilibrium expression?

Vanyuwa [196]

The equilibrium expression shows the ratio between products and reactants. This expression is equal to the concentration of the products raised to its coefficient divided by the concentration of the reactants raised to its coefficient. The correct equilibrium expression for the given reaction is:

H2CO3(aq) + H2O(l) = H3O+(aq) + HCO3-1(aq)

Kc = [HCO3-1] [H3O+] / [H2O] [H2CO3]

4 0

3 years ago