A chemist observed a gas being evolved in a chemical reaction and collected some

Question

A chemist observed a gas being evolved in a chemical reaction and collected some of it for analysis. It contains 80% C and 20% H. It was also observe that 500 ml. of the gas at 0 degree C and 760 torr weighed 0.6695 g What is the empirical formula of the gaseous compound? a CH b CH_2 c. CH_3 d.CH_4 c.C_2 H_2 What is the molecular weight of the gas? a. 26 b.30 c. 40 d. 50 e. 55 What is the molecular formula of the gas? a. C_2 H_2 b. C_2 H_4 c.C_2 H_6 d.C_2 H_8 c. C_3 H_8 What is the degree of hybridization for N in NCl_3 molecule? a. dsp^2 b. sp^2 c. sp^3 d dsp^3 e sp What is .he molarity of a solution containing 1.37 g of NaCl (formula weigh, 58.4) in 25.0 ml. of solution? a. 0 .120 M b. 0.0 598 M c. 0.179 M d. 0.0 154 M e. 0.938 M Sulfur combines with oxygen gas to form 6.4 grams of sulfur dioxide, SO_2, , with no reactants left over, determine the following. The percent by mass sulfur and oxygen in SO_2 are: a 27.3%S, 72.7% b. 50% S, 50% c.35% S, 65% 0 d 64%, S, 36% 0 e. 20%S, 80%0 In the CaCO3 rightarrow CaO + CO_2, 100 g of CaCO_3 is observed to decompose upon heating into 56 grams of CaO and 44 grams of CO_2. This is an illustration of a, the Law of Conservation of Matter c, the Law of Conservation of Energy e. the law of proportional mixtures b. the Law of Gravity d. the Law of Multiple Proportions Five grams (5.0 g) of H2 are mixed with 10.0 g of O2 to produce water 2H_2 + O2 2H_2 O) Answer the following questions: Which would be the limiting reactant? Which reactant is in excess? H_2, O_2 b. H_2 O, O_2 c. O_2, H_2 d. H_2, H_2 O

Explanation / Answer

assume a basis of 100 g of sample

m = 80 g C, 20 g are H

mol of C =mass/MW = 80/12 = 6.66

mol of H = mass/MW = 20/1 = 20

ratio

20/6.66 = 3

C1H3 , the empirical formula is C, CH3

Q24.

MW of gas = mass/mol

mass = 0.6695 g

mol = form idal gas law

PV = nRT

n = PV/(RT) = (760)(0.5)/(62.3*273)) = 0.022342 mol

MW = mass/mol = 0.6695/0.022342 = 29.96 g/mol, nearest value is 30 g/mol B

Q25.

Molar mass of empirical = 12+3 = 15

raito = 30/15 = 2

C2H6 is the formula

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