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3 years ago

In an experiment, how many variables should you change at a time? And why?

Chemistry

1 answer:

aleksandrvk [35]3 years ago

5 0

Answer:

it should test one variable at a time.

Explanation: because you will not be able to tell which variable is responsible for the observed results.

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Which is a physical property of milk?

RideAnS [48]

C, because Boiling doesnt change the substance, making it a Physical property

5 0

4 years ago

Before it was launched, a helium-filled balloon had a pressure of 101 kPa at a temperature of 20°C. At an altitude of 15 000 m,

bogdanovich [222]

Answer:

5.54 m³.

Explanation:

We should use the ideal gas law: PV = nRT,

where, P is the pressure of the gas in atm,

V is the volume of the gas in L,

n is the number of moles in mole,

R is the general gas constant (R = 0.082 L.atm/mol),

T is the temperature of the gas in K.

We have two different cases at different (P, V and T) while the number of moles of He and R is constants.

∴ (P₁V₁) / (T₁) = (P₂V₂) / (T₂).

We can use P in KPa and V in m³ that the conversion factor can be canceled by division, but we should use T in K because its conversion factor is additive value.

P₁ = 101.0 kPa, V₁ = ??? m³, and T₁ = (20 °C + 273) = 293.0 K.

P₂ = 11.7 kPa, V₂ = 35.4 m³, and T₂ = (-56 °C + 273) = 217 K.

∴ The initial volume (V₁) = (P₂V₂T₁) / (P₁T₂) = (11.7 kPa)(35.4 m³)(293.0 K) / (101.0 kPa)(217.0 K) = (121354.74) / (21917) = 5.537 m³ ≅ 5.54 m³.

7 0

3 years ago

Which bases can deprotonate acetylene? the pka values of the conjugate acids are given in parentheses. select all that apply. ch

Usimov [2.4K]

pKa is a value which is related to the acid dissociation constant Ka

pKa = -log Ka

i.e. Ka = 10^-pKa

The deprotonation reaction of acetylene is:

HC≡CH ↔ HC≡C⁻ + H⁺

pKa (HC≡CH) = 25

Solvents with pKa greater than 25 will deprotonate acetylene.

Ans: CH2=CH⁻ pka = 44 and CH3NH⁻ pka = 40

4 0

4 years ago

A reaction that involves reagent X as the limiting reagent is begun with an initial concentration of 0.732-M X. The reaction rea

katovenus [111]

Answer:

The answer to the question is 0.0122 m/s

Explanation:

The rate of a reaction is the measure of the change in concentration of a reagent within a specific time frame. Reaction rate of a substance can be calculated by finding the division of the concentration change of the substance and the time required to undergo the change in concentration.

$Average reaction rate \frac{Change in the moles count of X}{Change in time} =$

The initial number of moles of X = 0.732 moles and final number of moles of X = 0 moles and the time it took to effect the change = 60s

then the rate of reaction = $\frac{0.732}{60}$ = 0. 0122 moles per second

the rate of the reaction involving X = 0.0122 m/s

7 0

4 years ago

When the equation below is balanced with the smallest possible integer coefficients, what is the coefficient for PH3?

Vikki [24]

Answer:

The coefficient for PH3 is 8. Option D is correct.

Explanation:

Step 1: The unbalanced equation

P2H4(g) ⇆ PH3(g) + P4(s)

Step 2: Balancing the equation

P2H4(g) ⇆ PH3(g) + P4(s)

On the left side we have 4x H (in P2H4), on the right side we have 3x H (in PH3). To balance the amount of H on both sides, we have to multiply P2H4 on the left side by 3 and PH3 on the right by 4.

3P2H4(g ) ⇆ 4PH3(g) + P4(s)

On the left side we have 6x P (in 3P2H4) on the right side we have 8x P (4x in 4PH3 and 4x in P4). To balance the amount of P on bot hsides, we have to multiply 3P2H4 by 2 and 4PH3 also by 2. Now the equation is balanced

6P2H4(g ) ⇆ 8PH3(g) + P4(s)

The coefficient for PH3 is 8. Option D is correct.

5 0

4 years ago