A student measures the average atomic mass of an element to be 78.93 amu The actual atomic mass is 80.29 amu Calculate the students percent error round your answer to two decimal place

Percent error = -1.69%

Explanation:

Given data:

Measured value of average atomic mass = 78.93 amu

Actual  value of average atomic mass = 80.29 amu

Percent error = ?

Solution:

Formula:

Percent error = [measured value - actual value /actual value] × 100

Percent error = [ 78.93 amu - 80.29 amu/80.29 amu ] × 100

Percent error = [-1.36 /80.29 amu ] × 100

Percent error = -1.69%

Negative sign shows that measured value is less than actual value.

every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. therefore, there must be the same number of atoms of each element on each side of a chemical equation.

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2