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# Combustion Analysis and Concentration (Worksheet)

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Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

## Q1.

Combustion analysis of toluene a common organic solvent, gives 5.86 mg of $$CO_2$$ and 1.37 mg of $$H_2O$$. If the compound only contains carbon and hydrogen, what is its empirical formula?

2. Menthol is composed of C, H, and O. A 0.1005 g sample is combusted, producing 0.2829 g of $$CO_2$$ and 0.1159 g of $$H_2O$$. What is the empirical formula for menthol? If the compound has a molar mass of 156 g/mol, what is its molecular formula?

3. Combustion of 2.78 mg of ethyl butyrate produces 6.32 mg of $$CO_2$$ and 2.58 mg of $$H_2O$$. What is the empirical formula is the compound is composed of C, H, and O?

## Q4. Calculate

1. the number of grams of solute in 0.250 L of 0.150 M $$KBr$$
2. Molar concentration of a solution containing 4.75 g of $$Ca(NO_3)_2$$ in 0.200L
3. the volume of 1.50 M $$Na_3PO_4$$ in milliliters that contains 5.00 g of solute.

## Q5.

a. How many milliliter of a stock solution of 10.0 M $$HNO_3$$ would you have to use to prepare 0.350 L of 0.400 M $$HNO_3$$?

b. If you dilute 25.0 mL of the stock solution to a final volume of 0.500 L what will be the concentration of the diluted solution?

## Q6.

What mass of $$NaCl$$ is needed to precipitate the silver ions from 20.0 mL of 0.100 M $$AgNO_3$$ solution?

$NaCl_{(aq)} + AgNO_{3\; (aq)} \rightarrow NaNO_{3\;(aq)} + AgCl_{(s)}$

7. How many milliters of 0.120 M $$HCl$$ are needed to completely neutralize 50.0 mL of 0.101 M $$Ba(OH)_2$$ solution?

$2HCl + Ba(OH)_2 \rightarrow BaCl_2 + 2H_2O$