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Find the enthalpy change per mole of sodium when sodium reacts with water. 13 grams of sodium reacts with 247 cm3 of water, prod

Ierofanga [76]

The answer is

-79 kJ/mol

The explanation:

The reaction equation is:

2Na + 2H2O  2NaOH + H2

when ΔHrxn= -q

and q=cmΔT

where:

-q is amount of heat absorbed/released

-and c is specific heat of solution (in such calculation an assumption is made that c solution = c water)

- and m is mass of solution

- and ΔT is temperature change

1- now we need to Find mass of solution:

m solution = m(H2O)+ m(Na)-m(H2)m(H2O)

m H2O= V(H2O)*ρ(H2O)

= 247 cm3*1g/cm3 = 247 gm

and m(Na)= 13 g

2- now we need to Find m(H2):

n(Na)(moles Na)= mass/Molar mass = 13g/23 g/mol = 0.57 mol.

According to equation mole ratio n(Na):n(H2)= 2:1,

then n(H2)=n(Na)/2

=0.57/2=0.29 mol.

∴m(H2)= moles * molar mass

=0.29 mol *2g/mol

= 0.58 g

∴m solution= 247 g + 13 g – 0.58 g = 259.42 g

and when q=4.18 J/K g* 259.42 g *(339.7 K – 298 K)= 45218 J

The temperature of solution increased because heat was absorbed by the solution (q>0).

Then ΔHrxn= -q = -45218 J per 0.57 mol of Na

3- now we need to Find ΔHrxn per 1 mole of Na

ΔHrxn = -45218J/0.57 mol = -79331 J/mol ≈ -79 kJ/mol

4 0

3 years ago

Read 2 more answers

What is the volume of 6.78 mol of hydrogen gas at STP?

Marat540 [252]

Answer:

151.87dm³

Explanation:

Given parameters:

Volume of hydrogen gas = 6.78mole

Unknown:

Volume of hydrogen gas formed at STP = ?

Solution:

To solve this problem;

1 mole of a gas at STP = 22.4dm³ So;

6.78 mole of gas = 6.78 x 22.4 = 151.87dm³

7 0

3 years ago

The effect of nitogen and plants. Which factor is an independent variable

Yakvenalex [24]

The independent variable is what you are testing in the experiment - it sounds like the independent variable in this experiment is the amount/concentration of nitrogen

6 0

3 years ago

DUEEE IN 2 minutes!!

Julli [10]

Answer:

A acid. i hope this is right!

Explanation:

4 0

3 years ago

How many moles of tin, Sn, are in 2500 atoms of tin?

mario62 [17]

<h3>Answer:</h3>

4.2 × 10⁻²¹ moles Sn

<h3>General Formulas and Concepts:</h3>

<u>Pre-Algebra</u>

Order of Operations: BPEMDAS

Brackets
Parenthesis
Exponents
Multiplication
Division
Addition
Subtraction

Left to Right

<u>Chemistry</u>

<u>Atomic Structure</u>

Using Dimensional Analysis
Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.

<h3>Explanation:</h3>

<u>Step 1: Define</u>

2500 atoms Sn

<u>Step 2: Identify Conversions</u>

Avogadro's Number

<u>Step 3: Convert</u>

Set up: $\displaystyle 2500 \ atoms \ Sn (\frac{1 \ mol \ Sn}{6.022 \cdot 10^{23} \ atoms \ Sn})$
Multiply: $\displaystyle 4.15144 \cdot 10^{-21} \ moles \ Sn$

<u>Step 4: Check</u>

<em>Follow sig fig rules and round. We are given 2 sig figs.</em>

4.15144 × 10⁻²¹ moles Sn ≈ 4.2 × 10⁻²¹ moles Sn

6 0

2 years ago