CHEMISTRY MIDDLE SCHOOL

Please help me. Chemistry

Answers

Answer 1

Answer:

Answer:

element S is argon and element T is potassium.

4. B

5. D

Explanation:

in an element in periodic table number of elctrons and protons are same.

4. since element S has 18 protons so its atomic number must be 18 so the element is Argon which is the last element of period 4 so the next element will go to period 4 with one extra shell and since the atomic number of next element is 19 the element is Potassium. therefore T is Potassium.

5. number of nucleons in an atom is the number of protons and neutons combined together in an nucleus

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If 842 grams of sodium hydroxide reacts with 750.0 grams of aluminum, how many grams of aluminum hydroxide should theoretically form?

Answers

548.55 grams of aluminum hydroxide should theoretically form.

Explanation:

Balanced equation for the reaction:

3 NaOH + Al ⇒ Al(OH)3 +3 Na

DATA GIVEN:

mass of NaOH = 842 grams, atomic mass =39.9 grams/mole

mass of Al = 750 grams, atomic mass = 26.9 grams/mole

aluminum hydroxide theoretical yield = ?

Moles of NaOH reacted

number of moles = $(mass)/(atomic mass of 1 mole)$

putting the values in the equation

NaOH = $(842)/(39.9)$

= 21.1 MOLES OF NaOH

Al = $(750)/(26.9)$

= 27.8 moles

from the equation

from 3 moles of NaOH 1 mole of Al(OH)3 is produced

21.1 moles of NaOH will react to give x moles of Al(OH)3

$(1)/(3)$ = $(x)/(21.1)$

7.03 moles of Al(OH)3 is formed.

and

1 mole of Al(OH)3 is formed from 1 mole of Al in the reaction

so, 27.8 Moles will react to give give 27.8 moles of Al(OH)3 limiting reagent of the given reaction is NaOH

mass of Al(OH)3 =7.03 x 78 (atomic mass of Al(OH)3)

= 548.55 grams

theoretical yield from the given data is 548.55 grams

An object was measured by a worker as 17.4cm long, however, the manufacturer specifications list the length of the object at 17.9cm. What is the percent error in the workers measurements? ( In chemistry)

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Answer:

Percent error = 2.8

Explanation:

Given data;

Actual value = 17.9 cm

Measured value = 17.4 cm

Percent error = ?

Solution:

Formula:

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

Now we will put the values in formula:

Percent error = [17.9 cm - 17.4 cm / 17.9 cm] × 100

Percent error = [0.5 cm /17.9 cm] × 100

Percent error = 0.028 × 100

Percent error = 2.8

Answer:

2.79%

Explanation:

I clicked on 2.79% and it was correct.

Last question anyone??

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Answer:

3=8908-=698=49=304=+74950=405=0381=01=20

55555%

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Answers

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