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Write the correct symbol, with both superscript and subscript, for each of the following. Use the list of elements in the front inside cover as needed: (a) the isotope of platinum that contains 118 neutrons, (b) the isotope of krypton with mass number 84, (c) the isotope of arsenic with mass number 75, (d) the isotope of magnesium that has an equal number of protons and neutrons.

Summarize the evidence used by J. J. Thomson to argue that cathode rays consist of negatively charged particles.

(a) What isotope is used as the standard in establishing the atomic mass scale? (b) The atomic weight of boron is reported as 10.81, yet no atom of boron has the mass of 10.81 amu. Explain.

A chemist finds that 30.82 g of nitrogen will react with 17.60, 35.20, 70.40, or 88.00 g of oxygen to form four different compounds. (a) Calculate the mass of oxygen per gram of nitrogen in each compound. (b) How do the numbers in part (a) support Dalton’s atomic theory?

How does Dalton’s atomic theory account for the fact that when 1.000 g of water is decomposed into its elements, 0.111 g of hydrogen and 0.889 g of oxygen are obtained regardless of the source of the water?

Round each of the following numbers to four significant figures and express the result in standard exponential notation: (a) 102.53070, (b) 656.980, (c) 0.008543210, (d) 0.000257870, (e) –0.0357202.

In the year 2011, an estimated amount of 35 billion tons of carbon dioxide (CO₂) was emitted worldwide due to fossil fuel combustion and cement production. Express this mass of CO₂ in grams without exponential notation, using an appropriate metric prefix.

Peta is a metric prefix for 10¹⁵.

A solid white substance A is heated strongly in the absence of air. It decomposes to form a new white substance B and a gas C. The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. Based on these observations, can we determine whether solids A and B and gas C are elements or compounds? Explain your conclusions for each substance.

Give the chemical symbol or name for the following elements, as appropriate: (a) sulfur, (b) gold, (c) potassium, (d) chlorine, (e) copper, (f) U, (g) Ni, (h) Na, (i) Al, (j) Si.

Classify each of the following as a pure substance or a mixture. If a mixture, indicate whether it is homogeneous or heterogeneous: (a) rice pudding, (b) seawater, (c) magnesium, (d) crushed ice.

Concentrated hydrochloric acid HCl (M = 36.5 g/moL) is available as a solution with the weight fraction w of 36.0 % (density r = 1.179 g/mL at 20 °C).

Calculate the molar concentration of HCl in this solution.

 A student titrates an unknown monoprotic acid with a NaOH solution from a buret. After the addition of 12.35 mL of NaOH, the pH of the solution read 5.22. The equivalence point is reached at 24.70 mL of NaOH. What is the Ka of the acid?

Complete and balance the following molecular equations, and then write the net ionic equation for each:

(a) HBr(aq) + Ca(OH)₂(aq)
(b) Cu(OH)₂(s) + HClO₄(aq)
(c) Al(OH)₃(s) + HNO₃(aq)

Separate samples of a solution of an unknown salt are treated with dilute solutions of HBr, H₂SO₄, and NaOH. A precipitate forms in all three cases. Which of the following cations could be present in the unknown salt solution: K⁺, Pb²⁺, Ba²⁺?

Write balanced molecular and net ionic equations for the following reactions, and identify the gas formed in each. Express your answer as a balanced net ionic equation. Identify all of the phases in your answer.

1) Solid cadmium sulfide reacts with an aqueous solution of sulfuric acid

2) Solid magnesium carbonate reacts with an aqueous solution of perchloric acid