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3 years ago

Liquids tend to contract when heated. please select the best answer from the choices provided

Chemistry

2 answers:

pshichka [43]3 years ago

8 0

This statement is false. Everything expands when heated

likoan [24]3 years ago

7 0

B.False Reasoning for this is because when liquids are heated they tend to expand more, which then either turns into gas, or a solid when heated.

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Which allele for human blood type is recessive?

blagie [28]

O blood type is recessive hope this helps

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3 years ago

Read 2 more answers

Consider the following reaction: NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2 How many g of CO2 would be produced from the complete r

Alenkasestr [34]

<h2>1.25 g of $CO_2$ would be produced from the complete reaction of 25 mL of 0.833 mol/L $HC_3H_3O_2$ with excess $NaHCO_3$ </h2>

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in L)}}$

$0.833M=\frac{\text{Moles of} HC_3H_3O_2\times 1000}{25ml}\\\\\text{Moles of} HC_3H_3O_2 =\frac{0.833mol/L\times 25}{1000}=0.0208mol$

$NaHCO_3+HC_2H_3O_2\rightarrow NaC_2H_3O_2+H_2O+CO_2$

According to stoichiometry:

1 mole of $HC_2H_3O_2$ will give = 1 mole of $CO_2$

0.0208 moles of $HC_2H_3O_2$ will give = $\frac{1}{1}\times 0.0208=0.0208 moles$ of $CO_2$

Mass of $HC_2H_3O_2=moles\times {\text {molar mass}}=0.0208\times 60g/mol=1.25g$

Thus 1.25 g of $CO_2$ would be produced from the complete reaction of 25 mL of 0.833 mol/L $HC_3H_3O_2$ with excess $NaHCO_3$

Learn more about molarity

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5 0

3 years ago

50cm3 of 1 mol/dm3 HCl at 30°C was mixed with 50cm3 of 1mol/dm3 NaOH at 30°C in a styrofoam calorimeter. The temperature of the

trapecia [35]

Answer:

-21 kJ·mol⁻¹

Explanation:

Data:

H₃O⁺ + OH⁻ ⟶ 2H₂O

V/mL: 50 50

c/mol·dm⁻³: 1.0 1.0

ΔT = 4.5 °C

C = 4.184 J·°C⁻¹g⁻¹

C_cal = 50 J·°C⁻¹

Calculations:

(a) Moles of acid

$\text{Moles of acid} = \text{0.050 dm}^{3} \times \dfrac{\text{1.0 mol}}{\text{1 dm}^{3}} = \text{0.050 mol}\\\\\text{Moles of base} = \text{0.050 dm}^{3} \times \dfrac{\text{1.0 mol}}{\text{1 dm}^{3}} = \text{0.050 mol}$

So, we have 0.050 mol of reaction

(b) Volume of solution

V = 50 dm³ + 50 dm³ = 100 dm³

(c) Mass of solution

$\text{Mass of solution} = \text{100 dm}^{3} \times \dfrac{\text{1.00 g}}{\text{1 dm}^{3}} = \text{100 g}$

(d) Calorimetry

There are three energy flows in this reaction.

q₁ = heat from reaction

q₂ = heat to warm the water

q₃ = heat to warm the calorimeter

q₁ + q₂ + q₃ = 0

nΔH + mCΔT + C_calΔT = 0

0.050ΔH + 100×4.184×4.5 + 50×4.5 = 0

0.050ΔH + 1883 + 225 = 0

0.050ΔH + 2108 = 0

0.050ΔH = -2108

ΔH = -2108/0.0500

= -42 000 J/mol

= -42 kJ/mol

This is the heat of reaction for the formation of 2 mol of water

The heat of reaction for the formation of mol of water is -21 kJ·mol⁻¹.

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3 years ago

How do you calculate the number of valence electrons in an atom?

gavmur [86]

To find<span> the </span>valence electrons in an atom<span>, identify what group the element is in. An element in group 1A has 1 </span>valence electron<span>. For example, Li is in group 1A, so that means it has one </span>valence electron. If the element is in group 2A, then it has two valence electrons<span>.</span>

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3 years ago

Which substance can not be decomposed by a chemical change?

slamgirl [31]

The answer is (2) Copper. Because copper is consist of atom. If it is decomposed, the atom will be changed. While chemical change is just the break down and form of chemical bonds between atoms.

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3 years ago