The mass of a 25.850g piece of copper is measured three times with two different balances with following results

Trial Method 1 (g)

1) 25.747

2) 25.745

3) 25.748

Trial Method 2 (g)

1) 25.70

2)25.75

3) 25.71

c. Calculate the % error for each method. method 1 _________ method 2 _________ Which method is more precise? Explain your answer.

Thank you

An anctacid tablet was dissolved in 26.00ml of 0.650M HCl. The excess acid was back titrated with eactly 11.34ml of 1.05M NaOH. The average weight of a tablet is 0.834g. The tablet came from a bottle 150 tablets that cost $3.99.

a. Calculate the moles of HCl neutralized by the tablet. (moles of HCl(aq) neutralized per tablet = moles of HCl(aq) added to the antacid - moles of NaOH required to backtitrate)

b. Calculate the mass effectiveness of the antacid. (mass effectiveness = moles of HCl(aq) neutralized per tablet / mass of antacid (g))

c. Calculate the cost effectiveness of the antacid. (cost effectiveness = moles of HCl(aq) neutralized per tablet / price of tablet (cent))

An older naming system uses Latin names of the elements. For example, the Latin name of iron is ferrum (which gives iron its symbol of Fe). For metals that can have more than one charge, the Latin name takes a –ous ending for the smaller charge and an –ic ending for the larger charge. Based on these rules, what is the Latin name of Fe22​O33​?

A Ferrous oxide

B Ferric oxide

C Ferrum oxide

D Iron oxide

Aluminium oxide is a white , crystalline powder . it can be used as an adsorbent or a catalyst for organic reactions and is formed when aluminium reacts with oxygen . A mixture of 74.38g of Aluminium and 56.27 g oxygen gas is allowed to react.
...
1) write a balanced equation for the reaction above.
...
2) identify the limiting reactanct by showing the calculation .
..
3)determine the mass of the excess reactant present in the vessel when the reaction is complete.

1.What is the coordination number for each of the following complexes?

[Co(NH3)4Cl2]+

[Pb(EDTA)]2?

[Cu(NH3)4]2+

[Ag(NH3)2]NO3

2.What is the charge on each of the following complex ions?

hexaaquachromium(II), [Cr(H2O)6]?

tris(carbonato)ferrate(III), [Fe(CO3)3]?

diaquatetrabromovanadate(III), [V(H2O)2Br4]?

3.What is the oxidation number of the central metal ion in each of the following complexes?

[NiCl2Br2]2?

[Fe(H2O)2(NH3)4]3+

Na[Rh(CN)2]

The main defect in stoichiometric CsI is the Schottky defect. The fraction of lattice sites that exhibit Schottky defects as a function of temperature, is as follows: 1.08 x 10exp-16 at 300 K, 1.06 x 10exp-12 at 400 K, 2.63 x 10exp-10 at 500K, 1.04 x 10exp-8 at 600 K, 4.76 x 10exp-6 at 900 K. Show whether the formation of Schottky defects is given by an Arrhenius (or Boltzmann) expression and, if so, evaluate the enthalpy of formation of one Schottky defect and 1 mol of Schottky defects.

Does the Carboxylic acid of tyrosine get deprotonated by NaH? If so, why is it not alkylated by the alkyl halide? Comment on nucleophilic strength, and again use structures to explain your answer Alkyl halide is EtBr

The arsenic in a 1.27 g sample of a pesticide was converted to AsO3−4 by suitable chemical treatment. It was then titrated using Ag+ to form Ag3AsO4 as a precipitate.

A- What is the oxidation state of  As in AsO3−4?

B- Name Ag3AsO4 by analogy to the corresponding compound containing phosphorus in place of arsenic.

C- If it took 21.0 mL of 0.106 M Ag+ to reach the equivalence point in this titration, what is the mass percentage of arsenic in the pesticide?

Select two salts that dissolve in water to give a solution with pH <7.

A. CaF2

B. CH3 NH3 Cl

C. CrCl3

D. Sr(ClO4 ) 2

E. NaNO2

F. KNO3

Many transuranium elements, such as plutonium-232, have
very short half-lives. (For 232Pu, the half-life is 36 minutes.)
However, some, like protactinium-231 (half-life 5 3.34 3
104 years), have relatively long half-lives. calculate the change in energy when
1 mole of 232Pu nuclei and 1 mole of 231Pa nuclei are each
formed from their respective number of protons and neutrons.

PLEASE SHOW WORK, THANKS

Use the half reaction method to balance each of the following oxidation-reduction reactions. Identify the oxidizing agent and the reducing agent.

A) Cu(s) + Ag+(aq) ---> Ag(s) + Cu2+

B) Al(s) + I2(s) ---> AlI3(s)

C) Pb(s) + Fe3+(aq) ----> Pb2+(aq) + Fe(s)

What is the pH of a 0.250 M NaOCl solution? Kb = 3.4 x 10-7

what makes the noble gases "noble"?

Polonium crystallizes with a simple cubic structure. It has a density of 9.3 g/cm^3 , a radius of 167 pm, and a molar mass of 209 g/mol .
Estimate Avogadro's number (the number of atoms in one mole).

A hydrogen electron in the ground state absorbs a 92.3157 nm photon to reach a higher excited state (a), and then emits two photons, one with 1.75777 x 10^-20 J of energy to reach an intermediate state (b), and one with wavelength 1005.22nm as it falls back to a lower excited state (c). Determine the three energy levels (a,b,c) of this particular electron.