7. A compound is composed of carbon, hydrogen and oxygen. It was analysed and the folloWIng results were obtained: o Mass of sample = 30.50 g o Mass of carbon in sample = 12.08 g o Mass of hydrogen in sample 2.06 g a. Find its empirical formula. b. If the relative molecular mass of the compound is 180, find its molecular formula.

A substance X2Z has the composition (by mass) of 40.0% X and 60.0% Z. What is the composition (by mass) of the compound XZ2?

Atomic masses are relative masses. What does this mean?

When elemental carbon is burned in the open atmosphere, with plenty of oxygen gas present, the product is carbon dioxide. :math>C(s)+O2(g)CO2(g) wever, when the amount of oxygen present during the burning of the carbon is restricted, carbon monoxide is more likely to result. :math>2C(s)+O2(g)CO(g) at mass of each product is expected when a 5.00-g sample of pure carbon is burned under each of these conditions?

3.55 An average person inhales roughly 2.5 g of O2 in a minute. How many molecules of oxygen are inhaled in (a) 1 minute, (b) 1 hour, (c) 1 day by an average person?

A binary compound of magnesium and nitrogen is analyzed, and 1.2791 g of the compound ¡s found to contain 0.9240 g of magnesium. When a second sample of this compound is treated with water and heated, the nitrogen is driven off as ammonia, leaving a compound that contains 60.31% magnesium and 39.69% oxygen by mass. Calculate the empirical formulas of the two magnesium compounds.

3.79 Consider two samples. Sample A contains 2 moles of N2 and 1 mole of O2, and Sample B contains 1 mole of N2O5. (a) Which sample contains more molecules? (b) Which sample contains more oxygen atoms? (c) Which sample contains more nitrogen atoms?

Consider a hypothetical compound composed of elements X, Y, and Z with the empirical formula X2YZ3 . Given that the atomic masses of X, Y, and Z are 41.2, 57.7, and 63.9, respectively, calculate the percentage composition by mass of the compound. If the molecular formula of the compound is found by molar mass determination to be actually X4Y2Z6 , what is the percentage of each element present? Explain your results.

What is true about the chemical properties of the product? a. The properties are more like chemical A. b. The properties are more like chemical B. c. The properties are an average of those of chemical A and chemical B. d. The properties are not necessarily like either chemical A or chemical B. e. The properties arc more like chemical A or more like chemical B, but more information is needed. Justify your choice, and for choices you did not pick, explain what is wrong with them.

3.123 Most periodic tables provide molar masses with four or five significant figures for the elements. How accurately would you have to measure the mass of a sample of roughly 100 g to make a calculation of the number of moles of the chemical to have its significant figures limited by the molar mass calculation rather than the mass measurement?