Plz help with any of these problems...?

Question

Hydrogen gas and bromine gas react to form hydrogen bromide gas.

a. Write a balanced chemical equation for this reaction.

b. How many grams of hydrogen bromide gas can be produced from 3.2 g of hydrogen gas and 9.5 g of bromine gas?

c. How many grams of which reactant is left unreacted?

d. What volume of HBr, measured at STP, is produced in

When ammonia gas, oxygen gas and methane gas (CH4) are combined, the products are hydrogen cyanide gas and water.

a. Write a balance chemical equation for this reaction.

b. Calculate the mass of each product produced when 225 g of oxygen gas is reacted with an excess of the other two reactants.

c. If the actual yield of the experiment in b) is 105 g of HCN, calculate the percent yield.

Cinnamic acid contains only carbon, hydrogen and oxygen, and is found by analysis to be 73.0% C and 5.4% hydrogen. Find the empirical formula of this compound, the molar mass, and the molecular formula.

Thx alot

Answer 1

H2 + Br2 >> 2 HBr

Moles H2 = 3.2 / 2.016 g/mol =1.59

Moles Br2 = 9.5 / 159.808 g/mol = 0.0594 ( limiting reactant)

we get 2 x 0.0594 moles of HBr => 0.119 moles

Mass HBr = 0.119 mol x 80.912 g/mol =9.63 g

Moles H2 needed = 1.59 - 0.0594 = 1.53  => 1.53 mol x 2.016 g/mol = 3.08 g

V of HBr = 22.4 x 0.119 = 2.67 g

3NH3 + 2CH4 +3 O2 >>2 HCN +6 H2O

Moles O2 = 225 g / 32 g/mol = 7.0

moles HCN = 7.0 x 2 / 3 = 4.7

Mass HCN = 4.7 mol x 27 g/mol =127 g

moles H2O = 7.0 x 6 / 3 = 14

Mass water = 14 x 18 = 252 g

% yield = 105 x 100 / 127 = 82.7

Moles C = 73.0 / 12.011 = 6.08

moles H = 5.4 / 1.008 = 5.4

moles O = 21.6 / 16 = 1.35

6.08/ 1.35 =4.5 => C

5.4 / 1.35 = 4 =>H

1.35 / 1.35 = 1 => O

we multiply by 2 to get whole numbers

C9H8O2 is the formula